{"cve":"CVE-2026-77999","nvd":{"published":"2026-09-03T13:06:08.760","modified":"2026-09-03T17:30:37.197","status":"Deferred","description":"Joomla Extension - j2commerce.com - Unauthenticated PayPal callback forgery leading to order confirmation fraud in J2Store 1.0.0-3.3.21, 4.0.0-4.0.21, 4.1.0-4.1.6 - The PayPal IPN listener's signature check (`_validateIPN()`) accepted `UNVERIFIED` and any non-`INVALID` response as valid, made its verification request with `CURLOPT_SSL_VERIFYPEER` disabled, and stored its verdict in a field nothing downstream ever checked — so processing continued regardless of the outcome. Separately, the paid-amount comparison only ran when `mc_gross` was a positive number; omitting the field from the POST body (`floatval(null) == 0`) skipped the check entirely. Combined with a merchant-configured `receiver_email` and a sequential, enumerable order id read from the `custom` field, an anonymous POST was enough to move a pending order straight to `CONFIRMED` with no payment, or force another customer's pending order to `FAILED`. `paypalv2.php` performed no amount check under any circumstances.","cvss_v4":{"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","score":8.7},"cvss_v3":null,"cwes":["CWE-472","CWE-602"],"references":["https://www.j2commerce.com/"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:50:50.842544443+00:00"},"epss":{"cve":"CVE-2026-77999","score":0.00428,"percentile":0.37079,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}