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Advisories

XenForo < 2.3.13 Signature Verification Bypass via PayPal REST Webhook

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severity
high
date
Affecting

  • XenForo < 2.3.13

CWE
  • CWE-754 Improper Check for Unusual or Exceptional Conditions
CVSS
8.7
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
Credit
Marco Paciaroni (BomboBombone)
Description
XenForo before 2.3.13 contains a signature verification logic error in the PayPal REST webhook handler that allows unauthenticated attackers to bypass payment signature validation by submitting a webhook request with an unsupported auth_algo header value. When the algorithm cannot be mapped to a supported hash function, the verification function incorrectly returns true instead of failing, causing the caller to treat the fabricated request as verified and process the payment event without a valid PayPal signature.

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