Comments – wpDiscuz < 7.3.2 – Admin+ Stored Cross-Site Scripting | CVE 2021-24737

Description

The plugin does not properly sanitise or escape the Follow and Unfollow messages before outputting them in the page, which could allow high privilege users to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed.

Timeline:
May 18th, 2021 - Vendor contacted by email, not a security issue according to them but will filter in the next update.
September 7th, 2021 - v7.3.0 released, issue still present
September 13th, 2021 - Escalated to WP Plugins Team & Public Disclosure. v7.3.1 released, issue still present.
September 19th, 2021 - v7.3.2 released, fixing the issue when settings are saved again (so any existing payloads will still work until settings are saved with this new version installed)

Proof of Concept

Ad admin, put the following payload in the wpDiscuz > Phrases > Follow > "You started following this comment author" or "You stopped following this comment author" fields: </div><script>alert('XSS')</script>

Save the changes, log on with a user, go to a post with a comment from another user, and click the Follow/Unfollow icon (under a user comment profile picture) to trigger the XSS