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Cross-site Scripting occurrences in Codeigniter
CodeIgniter4 is the 4.x branch of CodeIgniter, a PHP full-stack web framework. A cross-site scripting (XSS) vulnerability was found in `API\ResponseTrait` in Codeigniter4 prior to version 4.1.8. Attackers can do XSS attacks if a potential victim is using `API\ResponseTrait`. Version 4.1.8 contains a patch for this vulnerability. There are two potential workarounds available. Users may avoid using `API\ResponseTrait` or `ResourceController` Users may also disable Auto Route and use defined routes only. (2022-01-24, CVE-2022-21715)
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>