The Stop Spammers WordPress plugin before 2021.9 did not escape user input when blocking requests (such as matching a spam word), outputting it in an attribute after sanitising it to remove HTML tags, which is not sufficient and lead to a reflected Cross-Site Scripting issue.

The Stop Spammers Security | Block Spam Users, Comments, Forms WordPress plugin before 2021.18 does not escape some of its settings, allowing high privilege users such as admin to set Cross-Site Scripting payloads in them even when the unfiltered_html capability is disallowed

The Stop Spammers Security | Block Spam Users, Comments, Forms WordPress plugin before 2022.6 passes base64 encoded user input to the unserialize() PHP function when CAPTCHA are used as second challenge, which could lead to PHP Object injection if a plugin installed on the blog has a suitable gadget chain

The Stop Spammers Security | Block Spam Users, Comments, Forms WordPress plugin before 2023 does not sanitise and escape various parameters before outputting them back in admin dashboard pages, leading to a Reflected Cross-Site Scripting which could be used against high privilege users such as admin

The Stop Spammers Security | Block Spam Users, Comments, Forms WordPress plugin before 2023 does not sanitise and escape some of its settings, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup)