FirefoxWeb browser · Mozilla
CVE-2016-1942
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 · uneditedMozilla Firefox before 44.0 allows user-assisted remote attackers to spoof a trailing substring in the address bar by leveraging a user's paste of a (1) wyciwyg: URI or (2) resource: URI.
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 confidenceMozilla Firefox before 44.0 contains an address bar spoofing vulnerability where a user-assisted attack (requiring user to paste a wyciwyg: or resource: URI) allows remote attackers to spoof trailing substrings in the displayed URL, potentially tricking users into believing they are on a different website than they actually are.
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
<= 43.0.4= 42.1= 13.1= 13.2CVSS 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
- Required
- Scope
- Changed
- Confidentiality
- None
- Integrity
- High
- Availability
- None
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:N
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.
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Determine installed Firefox versionIn Firefox, navigate to Help > About Firefox, or run 'firefox --version' from command line, or check package manager: 'rpm -q firefox' (RHEL/Fedora) or 'dpkg -l firefox' (Debian)Affected if Version is 43.0.4 or lower, or version cannot be determined and is assumed to be older than 44.0
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Check Firefox package version on OpensuseRun 'rpm -q firefox' or 'zypper se firefox' to query the installed Firefox package versionAffected if Opensuse Leap 42.1 or Opensuse 13.1/13.2 with Firefox version at or below 43.0.4 is installed
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Verify address bar behavior with wyciwyg: URIManually test by pasting 'wyciwyg://example.com/' into the address bar and observe whether the displayed URL correctly reflects the full URI schemeAffected if The address bar displays only a portion of the URI scheme or shows a different trailing substring than expected, indicating spoofing is possible
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Verify address bar behavior with resource: URIManually test by pasting 'resource://gre/res/hiddenWindow.html' or similar resource: URI into the address bar and observe URL displayAffected if The displayed URL in the address bar does not show the complete resource: URI or shows a misleading trailing portion
A user is affected if Firefox version is 43.0.4 or lower (or the version is unknown on affected Opensuse systems) and the browser processes wyciwyg: or resource: URIs in a way that allows trailing substring spoofing in the address bar.
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.
From vendor dataUpgrade to Firefox 44.0 or later to resolve the address bar spoofing vulnerability. Users should be cautioned against pasting unknown URIs into their browser address bar.
Fix this in Firefox
Scoped from the published advisory
- Consultation2.0 h
- Implementation3.0 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 $2,272.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2016-1942 — 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-2016-1942 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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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- 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
- No spam, self-promotion, credentials, or personal data