Happyforms < 1.22.0 - Contributor+ Stored XSS

The plugin does not validate and escape some of its block options before outputting them back in a page/post where the block is embed, which could allow users with the contributor role and above to perform Stored Cross-Site Scripting attacks.

PoC

Exploit Additional CSS class(es) for “Forms” Gutenberg block: " onmouseover=“alert(1)” style=“background:red;”