XSS (Cross Site Scripting) Vulnerability.
The ability to execute desired code in a user’s browser using client-based code embedding within HTML codes is known as XSS.
In a summary, XSS is the interstice scripting procedure. XSS is a type of attack rather than a vulnerability. When we talk about XSS, though, we’re referring about vulnerabilities that enable XSS attacks.
There are different types of XSS:
- Stored (persistent) XSS: This is the most dangerous XSS attack that is stored on the server and executed automatically. Although today’s web browsers have blocked many of these malicious codes, called payloads, at a basic level, it is still a critical shortcoming.
- Reflected XSS : in this case, the malicious code is not on the website itself, but is contained in a web link previously created by the attacker. This means that by processing this “bad” piece of code, which is taken over without checking and processing external parameters, the website can inadvertently break the data in the user’s browser or execute another script if the XSS installation itself is meant.
- DOM (Self) XSS: First of all, it is the abbreviation for the expression dom document object model. DOM includes everything that web browsers interpret at runtime. A method by which malicious code that is not displayed in the page source code is not sent to the server, but is immediately executed in the browser.
What this can lead to:
- Interference with the user’s session (cookies).
- Modifying a page to steal confidential data (e.g., a login/password registration form).
- Implementing scripts on high-traffic pages (for advertising, increasing views, DDoS attacks, and others).
- Deployment of malware on seemingly secure pages.
How you can protect yourself
- Paste data from a URL with parameters into the page after running it through multiple background (backend) filters.
- Note that character blocking is not enough, use protections with additional verification,
- Ensure secure data processing not only on the server side but also on the client side,
- Pass data through various control mechanisms without including them on the page, e.g., functions like htmlspecialchars, strip_tags, trim for PHP…