FirefoxWeb browser · Mozilla
CVE-2018-5116
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedWebExtensions 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceFirefox WebExtensions with the ActiveTab permission (prior to version 58) allowed access to cross-origin frames within the active tab, enabling malicious extensions to inject frames from arbitrary origins and interact with them in violation of same-origin policy expectations.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
FirefoxWeb browser
<= 57.0.4
Ubuntu LinuxOperating system
= 14.04= 16.04= 17.10CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
-
Check installed Firefox versionOpen Firefox, go to Help > About Firefox, or run `firefox --version` from command lineAffected if Version is 57.0.4 or earlier, or any version prior to 58.0
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Verify Firefox package version on UbuntuRun `dpkg -l | grep firefox` or check Software Center for installed firefox package versionAffected if Package version corresponds to Firefox 57.x or earlier (e.g., 57.0+build2 or similar)
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Identify WebExtensions using ActiveTab permissionExamine installed extensions: go to about:addons, click gear icon > Manage Extensions, or check ~/.mozilla/firefox/*.default/extensions/ for *.xpi files and inspect their manifest.json for 'activeTab' permissionAffected if Any extension with 'activeTab' permission in manifest.json is present and Firefox version is below 58
User is affected if Firefox version is 57.0.4 or any version below 58.0 and any WebExtension with ActiveTab permission is installed or loaded.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedUpgrade Firefox to version 58 or later to obtain the patched version that properly enforces same-origin restrictions for ActiveTab permission.
Firefox 58
- 1. Check current Firefox version by navigating to Help > About Firefox in the menu
- 2. Download Firefox 58 or later from the official Mozilla website (www.mozilla.org)
- 3. Run the installer and complete the installation process
- 4. Restart Firefox to ensure the update is fully applied
- 5. Verify the version is now 58 or higher via Help > About Firefox
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Firefox
Scoped from the published advisory
- Consultation2.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,408.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-5116 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2018-5116 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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