The vulnerability in YesWiki prior to version 4.6.7 is a stored cross-site scripting issue located in formatters/wakka.php. It arises when users who have editing or commenting privileges insert markdown image URLs containing quotes that break out of the src attribute. This manipulation allows the injection of onerror event handlers that execute JavaScript code in the context of the victim's browser session. The flaw can be exploited to run scripts when other users, including administrators, view the compromised content.

Successful exploitation can lead to the execution of arbitrary JavaScript in the browsers of users who view the injected content. This can result in information disclosure, session hijacking, or other client-side attacks. The vulnerability requires the attacker to have edit or comment posting privileges, limiting the scope of exploitation to authorized users. The CVSS score of 5.4 reflects a medium severity with low complexity and limited privileges required.

A fix is available in YesWiki version 4.6.7. Users and administrators should upgrade to version 4.6.7 or later to remediate this vulnerability. Until patched, restrict editing and commenting permissions to trusted users to reduce the risk of exploitation.