The Ultimate Blocks WordPress plugin before 3.1.7 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 Ultimate Blocks – WordPress Blocks Plugin plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's tab anchor metabox in all versions up to, and including, 3.0.8 due to insufficient input sanitization and output escaping on user supplied attributes. This makes it possible for authenticated attackers with contributor-level and above permissions to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.