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Cross-site Scripting occurrences in Mathjax
MathJax version prior to version 2.7.4 contains a Cross Site Scripting (XSS) vulnerability in the \unicode{} macro that can result in Potentially untrusted Javascript running within a web browser. This attack appear to be exploitable via The victim must view a page where untrusted content is processed using Mathjax. This vulnerability appears to have been fixed in 2.7.4 and later. (2018-07-23, CVE-2018-1999024)
Why Cross-site Scripting can be dangerous
Cross site scripting is an attack where a web page executes code that is injected by an adversary. It usually appears, when users input is presented. This attack can be used to impersonate a user, take over control of the session, or even steal API keys.
The attack can be executed e.g. when you application injects the request parameter directly into the HTML code of the page returned to the user:
https://server.com/confirmation?message=Transaction+Complete
what results in:
<span>Confirmation: Transaction Complete</span>
In that case the message can be modified to become a valid Javascript code, e.g.:
https://server.com/confirmation?message=<script>dangerous javascript code here</script>
and it will be executed locally by the user's browser with full access to the user's personal application/browser data:
<span>Confirmation: <script>dangerous javascript code here</script></span>