Posts Tagged ‘database security’

10 Most Common Web Security Vulnerabilities

For all too many companies, it’s not until after a breach has occurred that web security becomes a priority. During my years working as an IT Security professional, I have seen time and time again how obscure the world of IT Security is to so many of my fellow programmers.

An effective approach to IT security must, by definition, be proactive and defensive. Toward that end, this post is aimed at sparking a security mindset, hopefully injecting the reader with a healthy dose of paranoia.

In particular, this guide focuses on 10 common and significant web security pitfalls to be aware of, including recommendations on how they can be avoided. The focus is on the Top 10 Web Vulnerabilities identified by the Open Web Application Security Project (OWASP), an international, non-profit organization whose goal is to improve software security across the globe.

A little web security primer before we start – authentication and authorization

When speaking with other programmers and IT professionals, I often encounter confusion regarding the distinction between authorization and authentication. And of course, the fact the abbreviation auth is often used for both helps aggravate this common confusion. This confusion is so common that maybe this issue should be included in this post as “Common Web Vulnerability Zero”.

So before we proceed, let’s clearly the distinction between these two terms:

  • Authentication: Verifying that a person is (or at least appears to be) a specific user, since he/she has correctly provided their security credentials (password, answers to security questions, fingerprint scan, etc.).
  • Authorization: Confirming that a particular user has access to a specific resource or is granted permission to perform a particular action.

Stated another way, authentication is knowing who an entity is, while authorization is knowing what a given entity can do.

Common Mistake #1: Injection flaws

Injection flaws result from a classic failure to filter untrusted input. It can happen when you pass unfiltered data to the SQL server (SQL injection), to the browser (XSS – we’ll talk about this later), to the LDAP server (LDAP injection), or anywhere else. The problem here is that the attacker can inject commands to these entities, resulting in loss of data and hijacking clients’ browsers.

Anything that your application receives from untrusted sources must be filtered, preferably according to a whitelist. You should almost never use a blacklist, as getting that right is very hard and usually easy to bypass. Antivirus software products typically provide stellar examples of failing blacklists. Pattern matching does not work.

Prevention: The good news is that protecting against injection is “simply” a matter of filtering your input properly and thinking about whether an input can be trusted. But the bad news is that all input needs to be properly filtered, unless it can unquestionably be trusted (but the saying “never say never” does come to mind here).

In a system with 1,000 inputs, for example, successfully filtering 999 of them is not sufficient, as this still leaves one field that can serve as the Achilles heal to bring down your system. And you might think that putting an SQL query result into another query is a good idea, as the database is trusted, but if the perimeter is not, the input comes indirectly from guys with malintent. This is called Second Order SQL Injection in case you’re interested.

Since filtering is pretty hard to do right (like crypto), what I usually advise is to rely on your framework’s filtering functions: they are proven to work and are thoroughly scrutinized. If you do not use frameworks, you really need to think hard about whether not using them really makes sense in your environment. 99% of the time it does not.

Common Mistake #2: Broken Authentication

This is a collection of multiple problems that might occur during broken authentication, but they don’t all stem from the same root cause.

Assuming that anyone still wants to roll their own authentication code in 2014 (what are you thinking??), I advise against it. It is extremely hard to get right, and there are a myriad of possible pitfalls, just to mention a few:

  1. The URL might contain the session id and leak it in the referer header to someone else.
  2. The passwords might not be encrypted either in storage or transit.
  3. The session ids might be predictable, thus gaining access is trivial.
  4. Session fixation might be possible.
  5. Session hijacking might be possible, timeouts not implemented right or using HTTP (no SSL), etc…

Prevention: The most straightforward way to avoid this web security vulnerability is to use a framework. You might be able to implement this correctly, but the former is much easier. In case you do want to roll your own code, be extremely paranoid and educate yourself on what the pitfalls are. There are quite a few.

Common Mistake #3: Cross Site Scripting (XSS)

This is a fairly widespread input sanitization failure (essentially a special case of common mistake #1). An attacker gives your web application JavaScript tags on input. When this input is returned to the user unsanitized, the user’s browser will execute it. It can be as simple as crafting a link and persuading a user to click it, or it can be something much more sinister. On page load the script runs and, for example, can be used to post your cookies to the attacker.

Prevention: There’s a simple web security solution: don’t return HTML tags to the client. This has the added benefit of defending against HTML injection, a similar attack whereby the attacker injects plain HTML content (such as images or loud invisible flash players) – not high-impact but surely annoying (“please make it stop!”). Usually, the workaround is simply converting all HTML entities, so that <script> is returned as &lt;script&gt;. The other often employed method of sanitization is using regular expressions to strip away HTML tags using regular expressions on < and >, but this is dangerous as a lot of browsers will interpret severely broken HTML just fine. Better to convert all characters to their escaped counterparts.

Common Mistake #4: Insecure Direct Object References

This is a classic case of trusting user input and paying the price in a resulting security vulnerability. A direct object reference means that an internal object such as a file or database key is exposed to the user. The problem with this is that the attacker can provide this reference and, if authorization is either not enforced (or is broken), the attacker can access or do things that they should be precluded from.

For example, the code has a download.php module that reads and lets the user download files, using a CGI parameter to specify the file name (e.g., download.php?file=something.txt). Either by mistake or due to laziness, the developer omitted authorization from the code. The attacker can now use this to download any system files that the user running PHP has access to, like the application code itself or other data left lying around on the server, like backups. Uh-oh.

Another common vulnerability example is a password reset function that relies on user input to determine whose password we’re resetting. After clicking the valid URL, an attacker can just modify the username field in the URL to say something like “admin”.

Incidentally, both of these examples are things I myself have seen appearing often “in the wild”.

Prevention: Perform user authorization properly and consistently, and whitelist the choices. More often than not though, the whole problem can be avoided by storing data internally and not relying on it being passed from the client via CGI parameters. Session variables in most frameworks are well suited for this purpose.

Common Mistake #5: Security misconfiguration

In my experience, web servers and applications that have been misconfigured are way more common than those that have been configured properly. Perhaps this because there is no shortage of ways to screw up. Some examples:

  1. Running the application with debug enabled in production.
  2. Having directory listing enabled on the server, which leaks valuable information.
  3. Running outdated software (think WordPress plugins, old PhpMyAdmin).
  4. Having unnecessary services running on the machine.
  5. Not changing default keys and passwords. (Happens way more frequently than you’d believe!)
  6. Revealing error handling information to the attackers, such as stack traces.

Prevention: Have a good (preferably automated) “build and deploy” process, which can run tests on deploy. The poor man’s security misconfiguration solution is post-commit hooks, to prevent the code from going out with default passwords and/or development stuff built in.

Common Mistake #6: Sensitive data exposure

This web security vulnerability is about crypto and resource protection. Sensitive data should be encrypted at all times, including in transit and at rest. No exceptions. Credit card information and user passwords should never travel or be stored unencrypted, and passwords should always be hashed. Obviously the crypto/hashing algorithm must not be a weak one – when in doubt, use AES (256 bits and up) and RSA (2048 bits and up).

And while it goes without saying that session IDs and sensitive data should not be traveling in the URLs and sensitive cookies should have the secure flag on, this is very important and cannot be over-emphasized.


  • In transit: Use HTTPS with a proper certificate and PFS (Perfect Forward Secrecy). Do not accept anything over non-HTTPS connections. Have the secure flag on cookies.
  • In storage: This is harder. First and foremost, you need to lower your exposure. If you don’t need sensitive data, shred it. Data you don’t have can’t be stolen. Do not store credit card information ever, as you probably don’t want to have to deal with being PCI compliant. Sign up with a payment processor such as Stripe or Braintree. Second, if you have sensitive data that you actually do need, store it encrypted and make sure all passwords are hashed. For hashing, use of bcrypt is recommended. If you don’t use bcrypt, educate yourself on salting and rainbow tables.

And at the risk of stating the obvious, do not store the encryption keys next to the protected data. That’s like storing your bike with a lock that has the key in it. Protect your backups with encryption and keep your keys very private. And of course, don’t lose the keys!

Common Mistake #7: Missing function level access control

This is simply an authorization failure. It means that when a function is called on the server, proper authorization was not performed. A lot of times, developers rely on the fact that the server side generated the UI and they think that the functionality that is not supplied by the server cannot be accessed by the client. It is not as simple as that, as an attacker can always forge requests to the “hidden” functionality and will not be deterred by the fact that the UI doesn’t make this functionality easily accessible. Imagine there’s an /adminpanel, and the button is only present in the UI if the user is actually an admin. Nothing keeps an attacker from discovering this functionality and misusing it if authorization is missing.

Prevention: On the server side, authorization must always be done. Yes, always. No exceptions or vulnerabilities will result in serious problems.

Common Mistake #8: Cross Site Request Forgery (CSRF)

This is a nice example of a confused deputy attack whereby the browser is fooled by some other party into misusing its authority. A 3rd party site, for example, can make the user’s browser misuse it’s authority to do something for the attacker.

In the case of CSRF, a 3rd party site issues requests to the target site (e.g., your bank) using your browser with your cookies / session. If you are logged in on one tab on your bank’s homepage, for example, and they are vulnerable to this attack, another tab can make your browser misuse its credentials on the attacker’s behalf, resulting in the confused deputy problem. The deputy is the browser that misuses its authority (session cookies) to do something the attacker instructs it to do.

Consider this example:

Attacker Alice wants to lighten target Todd’s wallet by transfering some of his money to her. Todd’s bank is vulnerable to CSRF. To send money, Todd has to access the following URL:

After this URL is opened, a success page is presented to Todd, and the transfer is done. Alice also knows, that Todd frequently visits a site under her control at, where she places the following snippet:

<img src="" width="0" height="0" />

Upon visiting Alice’s website, Todd’s browser thinks that Alice links to an image, and automatically issues an HTTP GET request to fetch the “picture”, but this actually instructs Todd’s bank to transfer $1500 to Alice.

Incidentally, in addition to demonstrating the CSRF vulnerability, this example also demonstrates altering the server state with an idempotent HTTP GET request which is itself a serious vulnerability. HTTP GET requests must be idempotent (safe), meaning that they cannot alter the resource which is accessed. Never, ever, ever use idempotent methods to change the server state.

Fun fact: CSRF is also the method people used for cookie-stuffing in the past until affiliates got wiser.

Prevention: Store a secret token in a hidden form field which is inaccessible from the 3rd party site. You of course always have to verify this hidden field. Some sites ask for your password as well when modifying sensitive settings (like your password reminder email, for example), although I’d suspect this is there to prevent the misuse of your abandoned sessions (in an internet cafe for example).

Common Mistake #9: Using components with known vulnerabilities

The title says it all. I’d again classify this as more of a maintenance/deployment issue. Before incorporating new code, do some research, possibly some auditing. Using code that you got from a random person on GitHub or some forum might be very convenient, but is not without risk of serious web security vulnerability.

I have seen many instances, for example, where sites got owned (i.e., where an outsider gains administrative access to a system), not because the programmers were stupid, but because a 3rd party software remained unpatched for years in production. This is happening all the time with WordPress plugins for example. If you think they will not find your hidden phpmyadmin installation, let me introduce you to dirbuster.

The lesson here is that software development does not end when the application is deployed. There has to be documentation, tests, and plans on how to maintain and keep it updated, especially if it contains 3rd party or open source components.


  • Exercise caution. Beyond obviously using caution when using such components, do not be a copy-paste coder. Carefully inspect the piece of code you are about to put into your software, as it might be broken beyond repair (or in some cases, intentionally malicious).
  • Stay up-to-date. Make sure you are using the latest versions of everything that you trust, and have a plan to update them regularly. At least subscribe to a newsletter of new security vulnerabilities regarding the product.

Common Mistake #10: Unvalidated redirects and forwards

This is once again an input filtering issue. Suppose that the target site has a redirect.php module that takes a URL as a GET parameter. Manipulating the parameter can create a URL on that redirects the browser to When the user sees the link, they will see the user thinks is trusted and is safe to click. Little do they know that this will actually transfer them onto a malware drop (or any other malicious) page. Alternatively, the attacker might redirect the browser to

It is worth mentioning, that stuffing unsanitized user-defined input into an HTTP header might lead to header injection which is pretty bad.

Prevention: Options include:

  • Don’t do redirects at all (they are seldom necessary).
  • Have a static list of valid locations to redirect to.
  • Whitelist the user-defined parameter, but this can be tricky.


I hope that I have managed to tickle your brain a little bit with this post and to introduce a healthy dose of paranoia and web security vulnerability awareness.

The core takeaway here is that age-old software practices exist for a reason and what applied back in the day for buffer overflows, still apply for pickled strings in Python today. Security helps you write correct(er) programs, which all programmers should aspire to.

Please use this knowledge responsibly, and don’t test pages without permission!

For more information and more specific attacks, have a look at:

Feedback on this post is welcome and appreciated. Future related posts are planned, particularly on the issue of distributed denial-of-service (DDoS) and old-school (not web) IT security vulnerabilities. If you have a specific request on what to write about, please feel free to contact me directly at [email protected]


This post originally appeared on the Toptal Engineering Blog

The Role of WebRTC Technology In Online Security

WebRTC technology is rather new (spearheaded by Google in 2012 through the World Wide Web Consortium). It is a free project that provides browsers with Real-Time Communications. The technology is now widely used in live help customer support solutions, webinar platforms, chat rooms for dating, etc. But there are too little solutions for enhanced safety. It’s weird. Since this technology offers great opportunities in this field.

WebRTC opens great opportunities in secure communications online

In the case of WebRTC technology to create a communication channel between subscribers is used Peer to Peer method. At the same time, there is no data transfer to any server. It is a great advantage. This ensures the confidentiality of transmitted information.

The majority of modern communication services works through central server. It means that all history is stored on the server and third parties can get access to them.

Using WebRTC technology security provider developed a solution for confidential communication online in 2013. The main difference is the absence of data transfer to the server. Only the subscribers’ web browsers are used.


Chat service provides users with an opportunity to exchange messages by establishing a direct connection between their browsers and uses Peer to Peer method to communicate online.

To create a communication channel between subscribers it is enough to get a one-time key, and pass it to the called subscriber by any means of communication available. When the communication session is over, the history is deleted and the browser is closed, all correspondence between the subscribers disappears from the system.

In such case, no one can gain access to the content of communications.

A user will benefit from:

  • Secure text messaging
  • Secure Voice Call
  • Secure Video Call
  • Secure Data Transfer

As WebRTC supports not all browsers, Secure Chat solution works only in Google Chrome, Opera and Mozilla. At now developers are working on beta application for Android which will be available in Google Play Market in the nearest month.

Therefore, it is good chance for all us today to communicate securely online.

The Basics of Secure Web Development

The internet has contributed a great deal to commerce around the world in the last decade, and of course with a whole new generation of people breaking into the online world we’re starting to see just what computers are capable of accomplishing. Particularly when there is malicious intent on the other side of that keyboard.

Hackers and crackers are one of the biggest threats the world has ever experienced; they can take your money, your products or even destroy your business from the inside out – and you’ll never see them do it, they might not leave a trace at all. That is the terrifying truth about the internet; in most cases those with the skills to take what they want have the skills to hide themselves from detection – so what can you do to stop them.

The easiest way of protecting your website is to ensure that your business have a securely developed website. Secure web development is a complex area, and most likely something that you will need the help of a professional in order to fully implement, but it is worth noting that there are three different levels of security to take into consideration for your website and thus three different levels that need to be securely developed in order to ensure the protection of your business.

Consider these levels almost like doors. If your website was a business property you would have three ways in to the top secret bits; a front door, a side door and a back door.

The front door is the user interface; the bit of the website that you yourself work with. Now; the web developer might have made you a big magnificent door, lovely and secure – the sort of user interface that lets you manage your stock, orders, customers and all of the individual aspects of your business effortlessly without giving anything up. However; if your passwords aren’t secure it’s the equivalent of putting a rubbish, rusty old lock on that lovely secure door – completely pointless and insecure. Easy access. This is the first place a hacker is going to look – why would they waste their time hunting down and trying to exploit tiny weaknesses in the back door if they could open the front door with one little shove?

Change your passwords regularly, select passwords that use upper case, lower case, numbers and punctuation. Do not use the same password for everything.

The side door is the programming. The code used to construct your website puts everything in place and says who can do what and when; everything is controlled with the code, so an opening here can cause big problems if a hacker finds it. There are a number of different potential security risks when it comes to the code; there are bugs, which are just general, little faults with the website that occur when something didn’t go quite as planned or something was missed in the development stage. They always happen and there isn’t a single piece of software that doesn’t have bugs, the secure ones are just those that resolve the bugs as soon as they’re found, which stops them from being exploited.

Another risk to that side door is an injection; sort of like a fake key. This is something some of the smarter hackers can accomplish by injecting their own instructions into your system when it sends off a command or query – they can intercept your command or query. For example; let’s say you perform a simple PHP query that will fetch the products from the database when your user selects a product category. Normally this sort of script would be accessed through the URL with a category id.

For example;

Let’s say you did a regular sql database select query looking for the category ID, your category information and URL command might look something like;

c.category_id = ‘ . $_GET[‘cat’] . ‘LIMIT 10’;

Now; obviously this example suggests that the clever programmer has included a limit to prevent what is going to happen next – but this won’t protect him. Poor clever programmer is about to be outsmarted.

First of all; the only thing the thing the hacker needs to do is find your product list page and look for everything, example; or 1=1-

Doesn’t look like anything special right? Well, with this alone the hacker can now see every single one of your products. Depending on how secure your website is this might let them find faults in the products, but it’s probably still not that dangerous right? Well, what if they did this;

/productlist.php?cat=1 or error!;#$

Yep – bet you’re horrified now, because this will typically reveal the DBMS version of the query, and sometimes expose your table and column names. Not dangerous enough for you? With the tables and columns are revealed the hacker can move on to attacking the user table, all thanks to exploiting a weakness in the products table.

/productlist.php?cat=1 and (select count(*) from users) > 0

Creating a new query inside the existing one means that they don’t need to verify the database connection; they’re using yours. They have access to your database not and their using it to find your user table, which can progress to finding how many users you have, and even finding the information within the user table. I’m quite sure I don’t need to specify why having access to your user database is such a bad thing.

So – if you want to avoid the injections you need to ensure that every bit of input data gets validated, reduce the amount of information shown when an error displays, really limit the database permissions to prevent php queries from being able to pull any more information than they absolutely need to and use parameters in your queries.

Finally – the back door. This is the server. You need to ensure that the server you use to host your information and website is secure. There have been a number of cases where highly secure websites were eventually hacked by first hacking a much lower security website that shared the host server. If you want to avoid this you can consider a dedicated server for your website, you should also consider keeping to companies hosting companies that offer support and security as part of the hosting package. Ask them what software their servers are running; this will give you an idea of how regularly they are updated – up to date servers are the most secure. Older software has had longer to be exploited and thus more of the weaknesses in these are already known to hackers.



Kate Critchlow is a young and enthusiastic writer with a particular interest for technology, covering everything from secure development to the latest gadget releases.

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