CVE-2026-73316Public exploitNetwork attack vector

Unauthorized account upgrades via webhook replay

Published Sep 8, 2026 · Updated Sep 10, 2026

Payment replay in the PayPal REST provider in XenForo before 2.3.13 allows attackers to obtain unauthorized account upgrades. The provider's validateTransaction() override skips the base duplicate-transaction check, so the database accepts a previously processed transaction ID and runs purchase completion again. Exploitation requires one authentic, signed PayPal callback; replaying it can extend the same recurring upgrade more than once.

CVSS severity8.7
High
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Payment replay in the PayPal REST provider in XenForo before 2.3.13 allows attackers to obtain unauthorized account upgrades. The provider's validateTransaction() override skips the base duplicate-transaction check, so the database accepts a previously processed transaction ID and runs purchase completion again. Exploitation requires one authentic, signed PayPal callback; replaying it can extend the same recurring upgrade more than once.

The record

CVE
CVE-2026-73316
Published
Sep 8, 2026
Updated
Sep 10, 2026
Vendor
XenForo Ltd.
Product
XenForo
Classifications
CWE-345, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 10, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <2.3.13

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

XenForo Ltd. · XenForoversion=0 <2.3.13

Published CVSS scores

8.7VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-345Insufficient Verification of Data Authenticity
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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