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Fencer Intel
medium 5.3

CVE-2026-7686 json

eyeo Adblock Plus Legacy Premium Activation premium.preload.js postMessage access control

published 6mo ago modified 16d ago also EUVD-2026-26824

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 30%
public exploits
0
none known

Summary

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."

Patch / fix

Is CVE-2026-7686 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
6mo ago

Exploit prediction

0.36% chance of exploitation in the next 30 days, higher than 30% of all scored CVEs (FIRST EPSS, 2026-11-11).

Exploits and checks

  • github.com https://github.com/xryj920/CVE/blob/main/adblock_plus_CVE_report.md referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 6.9 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
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N/E:P/RL:O/RC:C
CNA 3.0 5.3 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N/E:P/RL:O/RC:C
CNA 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:P/A:N/E:POC/RL:OF/RC:C
CNA 4.0 5.5 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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
CNA 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:P/A:N

Affected products

  • eyeo Adblock Plus

Classification

Weakness
  • CWE-284 Improper Access Control
  • CWE-266 Incorrect Privilege Assignment

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.