Autoptimize <= 3.1.14 - Authenticated (Contributor+) Stored Cross-Site Scripting via Lazy-loaded Image Attributes

The Autoptimize plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the lazy-loading image processing in all versions up to, and including, 3.1.14. This is due to the use of an overly permissive regular expression in the `add_lazyload` function that replaces all occurrences of `\ssrc=` in image tags without limiting to the actual attribute. This makes it possible for authenticated attackers, with Contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page by crafting an image tag where the `src` URL contains a space followed by `src=`, causing the regex to break the HTML structure and promote text inside attribute values into executable HTML attributes.