The Qubely WordPress plugin before 1.8.5 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/b1aa6f32-c1d5-4fc6-9a4e-d4c5fae78389/