The OOPSpam Anti-Spam: Spam Protection for WordPress Forms & Comments (No CAPTCHA) plugin for WordPress is vulnerable to IP Header Spoofing in all versions up to, and including, 1.2.53. This is due to the plugin trusting client-controlled forwarded headers (such as CF-Connecting-IP, X-Forwarded-For, and others) without verifying that those headers originate from legitimate, trusted proxies. This makes it possible for unauthenticated attackers to spoof their IP address and bypass IP-based security controls, including blocked IP lists and rate limiting protections, by sending arbitrary HTTP headers with their requests.
The product does not use or incorrectly uses a protection mechanism that provides sufficient defense against directed attacks against the product.