Tag Archives: xss

When HTML Encoding Helped XSS

Recently I was pentesting a web app that had an unauthenticated XSS vulnerability but there was some heavy filtering in place. Nonetheless I was able to achieve session fixation using a combination of a technique I previously explained and some fun filter workarounds – including using the application’s own defensive HTML encoding to create a working XSS payload! Continue reading

Session Fixation and XSS Working Hand-in-Hand

Often a combination of security flaws come together to produce a unique attack vector. Individually the flaws may not amount to much but together they make an interesting combo. This is invariably more interesting from a pentesting point of view because you know that a tool couldn’t positively find it. Session fixation is one such scenario because usually a few requirements must be met for the attack to work. I thought I’d write up a recent session fixation flaw because the act of forcing the cookie onto the victim involved a little twist on overwriting session cookies that made a reflective XSS attack last a lot longer while also laughing in the face of httponly. Continue reading

A Tricky Case of XSS

On a recent test I came across a reflective XSS condition within a file upload page. When the extension was deemed invalid by the application, it was returned unsanitised within the error message. Not only did this turn out to be an exercise in exploiting reflective XSS in multipart/form-data but there were some pretty hefty restrictions on allowed characters too. Worthy of a post I thought. Continue reading

DOM XSS by Misusing Bootstrap

First of all, let me make it clear that this article is not about XSS in Bootstrap itself (the very popular libraries originally from Twitter to fancify your website), it’s about XSS as a result of using Bootstrap in an insecure fashion. It’s based on a real penetration test – the site in question wasn’t vulnerable but it was immediately clear how things could have gone wrong. I thought it would beĀ an interesting XSS article, being both DOM-based and making use of a big-name library like Bootstrap. Continue reading