Bleach clean() / Cleaner() fails to sanitize dangerous URI schemes in allowed formaction attributes

Summary Bleach clean / Cleaner fails to sanitize dangerous URI schemes in allowed formaction attributes. Bleach applies URI protocol sanitization only to attributes listed in attrvalisuri. While URI-bearing attributes such as action, href, src, and poster are included in that set, formaction is...

Cross-site Scripting (XSS)

Overview Affected versions of this package are vulnerable to Cross-site Scripting XSS via the clean function. An attacker can execute arbitrary JavaScript code in the context of the user's browser by submitting crafted HTML containing a formaction attribute with a dangerous URI scheme such as...