Spectra Gutenberg Blocks <= 2.19.25 - Authenticated (Contributor+) Remote Code Execution via Arbitrary PHP Function Call via Block Attributes

The Spectra Gutenberg Blocks – Website Builder for the Block Editor plugin for WordPress is vulnerable to Remote Code Execution in all versions up to, and including, 2.19.25. This makes it possible for authenticated attackers, with Contributor-level access and above, to execute code on the server. Exploitation requires a two-block payload embedded in post content: the first block registers a fake uagb/-prefixed block type with an attacker-specified render_callback, and the second block of the same fake type triggers invocation of that callback via call_user_func() during sequential block rendering in the same page request.