CVE-2026-77999

J2Store (Joomla extension by j2commerce.com) versions 1.0.0–3.3.21, 4.0.0–4.0.21, and 4.1.0–4.1.6 contain an unauthenticated PayPal callback forgery vulnerability. The IPN listener's signature check (_validateIPN()) treated UNVERIFIED and any non-INVALID response as valid, issued verification wit...