It was possible to exploit an Unauthenticated Time-Based Blind SQL Injection vulnerability in the Spam protection, AntiSpam, FireWall by CleanTalk WordPress Plugin before 5.153.4. The update_log function in lib/Cleantalk/ApbctWP/Firewall/SFW.php included a vulnerable query that could be injected via the User-Agent Header by manipulating the cookies set by the Spam protection, AntiSpam, FireWall by CleanTalk WordPress plugin before 5.153.4, sending an initial request to obtain a ct_sfw_pass_key cookie and then manually setting a separate ct_sfw_passed cookie and disallowing it from being reset.