GFI MailEssentials AI < 22.4 Anti-Spam Spam Keyword Checking Subject Condition Stored XSS

GFI MailEssentials AI versions prior to 22.4 contain a stored cross-site scripting vulnerability in the Spam Keyword Checking (Subject) conditions interface. An authenticated user can supply HTML/JavaScript in the ctl00$ContentPlaceHolder1$pvSubject$TXB_SubjectCondition parameter to /MailEssentials/pages/MailSecurity/ASKeywordChecking.aspx, which is stored and later rendered in the management interface, allowing script execution in the context of a logged-in user.