MonsterInsights < 8.12.1 - Contributor+ Stored XSS

The plugin 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.

As a contributor, add an "Inline Popular Posts" to a page/post and put the following payload in the Additional CSS class settings of the block: 

" onmouseover="alert(/XSS/)" style="background:red;"