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Fencer Intel
critical 9.8

CVE-2018-5116 json

WebExtensions with the "ActiveTab" permission are able to access frames hosted within the active tab even if the frames are cross-origin.

published 2018-06-11 8 y ago modified 2026-06-17 4 mo ago also EUVD-2018-16902

cvss
9.8
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.1%
EPSS 1.1% chance of exploitation in 30 days, percentile 66%
public exploits
0
none known

Summary

WebExtensions with the "ActiveTab" permission are able to access frames hosted within the active tab even if the frames are cross-origin. Malicious extensions can inject frames from arbitrary origins into the loaded page and then interact with them, bypassing same-origin user expectations with this permission. This vulnerability affects Firefox < 58.

Patch / fix

  • Mozilla Firefox 58
  • firefox Ubuntu 14.04 LTS 58.0+build6-0ubuntu0.14.04.1
  • firefox Ubuntu 16.04 LTS 58.0+build6-0ubuntu0.16.04.1
  • firefox Ubuntu 18.04 LTS 59.0.1+build1-0ubuntu1

ubuntu advisories UBUNTU-CVE-2018-5116

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • firefox-esr openSUSE Tumbleweed 128.5.1-1.1
  • MozillaFirefox openSUSE Tumbleweed 92.0-1.2

opensuse advisories openSUSE-SU-2024:14572-1openSUSE-SU-2024:10600-1

Exploit prediction

1.14% chance of exploitation in the next 30 days, higher than 66% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.0 9.8 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

Affected products

  • Mozilla Firefox

Classification

Weakness

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.