EWWW Image Optimizer < 8.7.7 - Author+ Stored XSS via Image Class Attribute Backreference Expansion

The EWWW Image Optimizer WordPress plugin before 8.7.7 does not properly escape image attribute values when it rewrites page output, allowing authenticated users with author-level access and above to inject arbitrary JavaScript that is stored in published content and executes in the browser of any user who later views the affected page.