Stored XSS

Stored or persistent XSS is a sub-type of XSS vulnerability and differs from reflected XSS by the fact that it is persistent in nature. It means that the payload, once inserted into a page, will stay and execute permanently on the page. This is sneakier than its reflected counterpart as most of the time the victim is simply unaware of the fact that a malicious code is running inside the affected website, making it a perfect choice for XSS worms. I hope some of you may be aware of the Samy worm which exploited a weak XSS filter in MySpace to create a persistent XSS scenario in which thousands of victims unknowingly executed the wormable JavaScript code, which further spread the code. Stored XSS vulnerability is pretty common in places where data is saved for a longer time, for example, in places such as comment sections, messaging, and similar places. They are a welcoming location to check for stored XSS issues.

Demonstrating stored XSS

Before proceeding to a few case studies on...