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Fencer Vulns
high 7.8

CVE-2018-5105 json

WebExtensions can bypass user prompts to first save and then open an arbitrarily downloaded file.

published 2018-06-11 8 y ago modified 2026-06-17 4 mo ago also EUVD-2018-16891

cvss
7.8
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 36%
public exploits
0
none known

Summary

WebExtensions can bypass user prompts to first save and then open an arbitrarily downloaded file. This can result in an executable file running with local user privileges without explicit user consent. 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-2018-5105

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

0.41% chance of exploitation in the next 30 days, higher than 36% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.0 7.8 CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
NVD 2.0 7.2 AV:L/AC:L/Au:N/C:C/I:C/A:C

Affected products

  • Mozilla Firefox

References

Sources

Fencer Vulns 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.