The Ultimate Blocks WordPress plugin before 3.1.9 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/a0dc73b3-3c51-4d03-963f-00fa7d8b0d51/