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CVE-2026-77999— 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

Quick assessment

Affected
j2commerce.com J2Store extension for Joomla
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

以下是该漏洞描述的中文翻译： Joomla 扩展 j2commerce.com —— J2Store 1.0.0-3.3.21、4.0.0-4.0.21、4.1.0-4.1.6 中未经验证的 PayPal 回调伪造，导致订单确认欺诈 PayPal IPN 监听器的签名校验函数（ ）将 及任何非 的响应都视为有效；其验证请求中禁用了 （SSL 证书对等体校验），并且将验证结果存储在一个下游流程从未检查的字段中——因此无论验证结果如何，后续处理都会继续执行。此外，已付金额的比较逻辑仅在 为正数时才会执行；如果从 POS

CVSS 8.7 · High EPSS 0.25% · P17

Affected Version Matrix 3

VendorProduct Version RangeStatus
j2commerce.com J2Store extension for Joomla 1.0.0-3.3.21 affected
4.0.0-4.0.21 affected
4.1.0-4.1.6 affected
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I. Basic Information for CVE-2026-77999

Vulnerability Information
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Vulnerability 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
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
对假设不可变Web参数的外部可控制
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
j2commerce.com J2Store extension for Joomla 1.0.0-3.3.21 -

II. Public POCs for CVE-2026-77999

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III. Intelligence Information for CVE-2026-77999

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Vendor Pages for CVE-2026-77999 (1)

Same Patch Batch · j2commerce.com · 2026-09-03 · 5 CVEs total

CVE-2026-78069 9.5 CRITICAL Joomla Extension - j2commerce.com - Missing authorization on Apps controller delegation ch
CVE-2026-78064 8.8 HIGH Joomla Extension - j2commerce.com - Anonymous cart-record tampering via inherited FOF `sav
CVE-2026-78065 7.1 HIGH Joomla Extension - j2commerce.com - Guest checkout address disclosure to any authenticated
CVE-2026-78000 5.3 MEDIUM Joomla Extension - j2commerce.com - Open redirect in cart controller in J2Store 1.0.0-3.3.

IV. Related Vulnerabilities

Same product: J2Store extension for Joomla
Same vendor: j2commerce.com
Same weakness: CWE-472

V. Comments for CVE-2026-77999

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