# CVE-2026-121636: Quick Event Manager 9.9.5 - 9.18 - Unauthenticated PayPal IPN Verification Bypass via the 'debug' Parameter

Status: published. Published: 2026-11-06. Updated: 2026-11-06.

The Quick Event Manager WordPress plugin before 9.19 does not verify the authenticity of PayPal payment notifications before marking event registrations as paid, which could allow unauthenticated attackers to mark registrations as paid without making a payment.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Unknown / Quick Event Manager: ≥ 9.9.5; < 9.19 (affected, semver). Source: CNA: WPScan

## Severity and prioritization

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N; source: CNA: WPScan

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-345

## Exploit evidence

- exploit: https://wpscan.com/vulnerability/04b181e1-639c-476f-b66b-2a073bf36829/ (CNA: WPScan)

## References

- https://wpscan.com/vulnerability/04b181e1-639c-476f-b66b-2a073bf36829/ (CNA: WPScan; exploit, vdb-entry, technical-description)

## Provenance

- CNA: WPScan: https://www.cve.org/CVERecord?id=CVE-2026-121636; retrieved 2026-11-06; source updated 2026-11-06

Revision: 00db0f3098c21931340a567bdd71a660ae6672b2cb64446c4fbbd21e3cf7f901

Canonical: https://y2.dev/cve/CVE-2026-121636

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.