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What is Cross-Site Scripting and How to Prevent it!

What is Cross-Site Scripting and How to Prevent it!

what-is-cross-site-scripting-and-how-to-prevent-itDigital landscape has changed very much in the past couple of years. New discoveries, innovations and technologies enchant us every day. Still, as much as we would like to believe, the digital world is not the wonderland. Emerging technologies bring with them emerging threats which are very difficult to discover, and mitigate. Having this in mind, you might think that there couldn’t be a bright side, but there is. Even though cyber threats are more advanced, harder to detect and to prevent, we should take this as a challenge and motivate ourselves to work smarter and find new and better solutions to solve the problems.

Cross-Site Scripting (XSS)

Maybe you’ve heard the term of Cross-Site Scripting or if not, you might have experienced it. Basically, Cross-Site Scripting, or XSS is a cyber-attack in which a user’s Web browser is tricked into regarding a “script” as coming from a legitimate website or web application when it has actually been slipped in from a malicious source. This happens when a web application uses unvalidated user input within the output it generates. A recent study revealed that 47% of WordPress vulnerabilities are Cross Site Scripting.

Let’s have a look at the potential impact of XSS:

  • Get access all the cookies and control the browser remotely
  • Get access to all the user sees and capture sensitive and private information.  
  • Bypass of all CSRF – protections and gain admin control.
  • Scan and exploit intranet appliances and applications

Basically, if the user executes the XSS, the attacker will be able to hijack the account, steal sensitive information and credentials, and much more.

However, as we all know that every cloud has its silver lining, Cross-Site Scripting has its own. In this case, I am talking about access to information and all that it provides. More important, we can learn from each other’s experiences and improve our strategies along the road.

As any self-respecting cyber-attack, XSS comes in different shapes and colours:

    • Non-Persistent Cross-site scripting attack, when the injected data is reflected in the response
    • Persistent cross-site scripting attack, when XSS vectors are stored in the website database and executed when a page is opened.
  • DOM-based cross-site scripting attack, when the XSS vector runs as a result of a DOM modification on a website in a user’s browser.

Now that we’ve hashed over what Cross-Scripting is and what are its impacts, let’s get to the interesting part.

How to prevent it Cross-Site Scripting attacks

  • Make sure that all variable output in a page is encoded before being returned to the end user
  • Convert each character to its HTML entity to make sure that the malicious scripting code is not an output as part of the page
  • Pass all external data through a filter to remove suspicious keywords, for instance, JavaScript commands, <SCRIPT> tag,

Bottom line, Cross-Site Scripting attacks are not that hard to prevent, as long as you keep an eye on some best practices and guidelines. In this article, I constantly gather recommendations from top security researchers and hope they’ll keep you safe! Enjoy the article!

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