The Ultimate Blocks WordPress plugin before 3.2.4 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/9342c6a1-4f9a-45f3-911d-0dfee4657243/