The Countdown Timer for WordPress Block Editor WordPress plugin through 1.0.5 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.

The Countdown Timer WordPress plugin through 1.0 does not sanitise and escape a parameter before outputting it back in the page, leading to a Reflected Cross-Site Scripting which could be used against high privilege users such as admin