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.

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact High

Vulnerable System Availability Impact None

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

No CVSS v3.1

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Exploitation none

Automatable yes

Technical Impact partial

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
j2commerce.com J2Store extension for Joomla unaffected
Version Status Constraints
1.0.0-3.3.21 affected —
4.0.0-4.0.21 affected —
4.1.0-4.1.6 affected —

No data.

No data.

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Vendors Products
J2commerce.com Subscribe
J2store Extension For Joomla Subscribe

Project Subscriptions

Vendors Products
J2commerce.com Subscribe
J2store Extension For Joomla Subscribe
Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://www.j2commerce.com/ cve-icon cve-icon
History

Thu, 03 Sep 2026 14:00:00 +0000

Type Values Removed Values Added
First Time appeared J2commerce.com
J2commerce.com j2store Extension For Joomla
Vendors & Products J2commerce.com
J2commerce.com j2store Extension For Joomla

Thu, 03 Sep 2026 13:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Thu, 03 Sep 2026 12:00:00 +0000

Type Values Removed Values Added
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.
Title 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
Weaknesses CWE-472
CWE-602
References
Metrics cvssV4_0

{'score': 8.7, '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'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: Joomla

Published:

Updated: 2026-09-03T12:40:09.757Z

Reserved: 2026-08-21T19:23:55.924Z

Link: CVE-2026-77999

cve-icon Vulnrichment

Updated: 2026-09-03T12:25:49.147Z

cve-icon NVD

Status : Deferred

Published: 2026-09-03T13:06:08.760

Modified: 2026-09-03T17:30:37.197

Link: CVE-2026-77999

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-03T13:45:04Z

Weaknesses