The Responsive iframe WordPress plugin through 1.2.0 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.
https://wpscan.com/vulnerability/fe2e47f4-b89e-4c22-8d27-672da0fb99af/