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Cross-site Scripting occurrences in Litespeed Cache
The LiteSpeed Cache WordPress plugin before 4.4.4 does not escape the qc_res parameter before outputting it back in the JS code of an admin page, leading to a Reflected Cross-Site Scripting (2022-01-03, CVE-2021-24963)
The LiteSpeed Cache WordPress plugin before 4.4.4 does not properly verify that requests are coming from QUIC.cloud servers, allowing attackers to make requests to certain endpoints by using a specific X-Forwarded-For header value. In addition, one of the endpoint could be used to set CSS code if a setting is enabled, which will then be output in some pages without being sanitised and escaped. Combining those two issues, an unauthenticated attacker could put Cross-Site Scripting payloads in pages visited by users. (2022-01-03, CVE-2021-24964)
A cross-site scripting (XSS) vulnerability in the LiteSpeed Cache plugin before 3.6.1 for WordPress can be exploited via the Server IP setting. (2020-12-26, CVE-2020-29172)
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>