CVE-2026-121636

Quick Event Manager 9.9.5 - 9.18 - Unauthenticated Unpaid Event Registration Confirmation

2026-11-04 00:00

Strategic Overview

Status: Patched in 9.19
Affected Plugin: Quick Event Manager
Affected Version: 9.9.5 – 9.18
CVSS: 5.3Medium
Weakness type: CWE-345 · Insufficient Verification of Data Authenticity
CVE: CVE-2026-121636

View all Quick Event Manager vulnerabilities

At a glance

CVE-2026-121636 is a medium-severity Insufficient Verification of Data Authenticity vulnerability in the Quick Event Manager WordPress plugin, affecting versions 9.9.5 – 9.18. It carries a CVSS score of 5.3 (reachable over the network; low attack complexity). Exploitation requires no authentication. The issue is fixed in version 9.19; sites on affected versions should update now. Disclosed November 2026, reported by Naoki Kawahigashi.

Vulnerability Overview

The Quick Event Manager plugin for WordPress is vulnerable to Authentication Bypass in versions 9.9.5 through 9.18. This is due to missing authentication check on the debug code path in the PayPal IPN handler, allowing any unauthenticated request with the ?debug parameter to bypass PayPal verification and have the status treated as VERIFIED. This makes it possible for unauthenticated attackers to mark event registrations as paid without making a payment by sending a crafted request with the debug parameter to bypass PayPal IPN verification.

Technical Analysis

The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no privileges on the target site, and no interaction from a victim user.

CWE-345: Insufficient Verification of Data Authenticity

The product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data.

Remediation

Update to version 9.19, or a newer patched version

How does WordSec protect against this?

This one needs no account at all, which puts it outside what login hardening can reach; WordSec's login security narrows the account-level paths around it, and the firewall is what inspects the request itself. None of that substitutes for the fix: Quick Event Manager 9.19 closes this, and updating the plugin is the step that ends it.

Login Security
Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2026-121636 https://www.wordfence.com/threat-intel/vulnerabilities/id/ed65b850-0e1c-43ce-82c4-c3f875ed0443 https://nvd.nist.gov/vuln/detail/CVE-2026-121636

Related records

Other vulnerabilities in Quick Event Manager

CVSS Vector

5.3

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Base

Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredNone
User InteractionNone
ScopeUnchanged
ConfidentialityNone
IntegrityLow
AvailabilityNone

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