YesWiki is a wiki system written in PHP. Prior to version 4.5.4, the "/?BazaR" endpoint and "idformulaire" parameter are vulnerable to cross-site scripting. An attacker can use a reflected cross-site scripting attack to steal cookies from an authenticated user by having them click on a malicious link. Stolen cookies allow the attacker to take over the user’s session. This vulnerability may also allow attackers to deface the website or embed malicious content. This issue has been patched in version 4.5.4.