The SP Page Builder (Pro) extension for Joomla contains a security flaw where the optin_form addon relies on untrusted input from the request to determine CAPTCHA parameters. This results in the CAPTCHA verification being reduced to a comparison of md5($captcha_question) != $captcha_answer, with both values attacker-controlled. Consequently, attackers can bypass CAPTCHA protections without authentication by crafting requests that manipulate these parameters. The affected versions include 5.1.4 through 6.9.0. The CVSS 4.0 base score is 6.9, indicating a medium severity vulnerability.

An unauthenticated attacker can bypass CAPTCHA protections, potentially allowing automated or scripted interactions that the CAPTCHA was intended to prevent. This could lead to abuse of forms or features protected by CAPTCHA in the affected Joomla extension. There is no indication of further privilege escalation or direct system compromise from this vulnerability alone.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, users should consider disabling the vulnerable optin_form addon or implementing additional server-side validation to prevent CAPTCHA bypass. Monitor the vendor's announcements for patches or updates addressing this issue.