CVE-2026-65879 is a critical security vulnerability in the SP Page Builder extension for Joomla (versions 1.0.0 to 6.7.0) caused by a hardcoded, product-wide secret. This secret enables unauthenticated attackers to perform mail relay attacks by forging the 'from' address in form submissions. The vulnerability impacts confidentiality, integrity, and availability, as reflected by its CVSS 3.1 score of 9.8. No official patch or remediation level has been disclosed by the vendor at the time of this report.

Exploitation of this vulnerability allows unauthenticated attackers to send emails with forged 'from' addresses via the vulnerable Joomla extension. This can facilitate phishing, spam, or other malicious email activities, potentially damaging the reputation of affected domains and compromising trust. The CVSS score indicates high impact on confidentiality, integrity, and availability, but no known exploits are reported in the wild yet.

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 affected extension or restricting access to forms that could be abused for mail relay. Monitor vendor communications for updates on patches or official mitigations.