FirefoxWeb browser · Mozilla
CVE-2018-12400
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 · uneditedIn private browsing mode on Firefox for Android, favicons are cached in the cache/icons folder as they are in non-private mode. This allows information leakage of sites visited during private browsing sessions. *Note: this issue only affects Firefox for Android. Desktop versions of Firefox are unaffected.*. This vulnerability affects Firefox < 63.
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 confidenceIn private browsing mode on Firefox for Android, favicons are incorrectly cached in the cache/icons folder as they are in non-private mode. This allows any application with filesystem access to read cached favicons and enumerate which websites were visited during private browsing sessions, leaking sensitive browsing history.
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
< 63.0CVSS 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
- Low
- Integrity
- None
- Availability
- None
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/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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Confirm Firefox for Android is installedCheck the device's installed applications for Mozilla Firefox specifically for the Android platform. This vulnerability only affects Firefox for Android, not Firefox desktop.Affected if The device has Firefox for Android installed
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Identify Firefox for Android versionGo to Settings > Apps > Mozilla Firefox and check the version number, or open Firefox and navigate to about:config to view the version. Compare against 63.0.Affected if The installed version is earlier than 63.0 (e.g., 62.x, 61.x, etc.)
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Locate Firefox cache directory on AndroidUsing a file manager or ADB shell, navigate to /data/data/org.mozilla.firefox/files/mozilla/ or /sdcard/Android/data/org.mozilla.firefox/files/mozilla/ and look for the cache folder.Affected if The cache directory exists and is accessible (requires root or filesystem access)
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Inspect cache/icons folder for faviconsWithin the cache directory, navigate to the icons subfolder. List all files present. Each favicon file typically corresponds to a visited website.Affected if The cache/icons folder contains .png or .ico files after private browsing sessions have been used
A user is affected if they have Firefox for Android version below 63.0 installed and the cache/icons folder contains favicon files that persist after using private browsing mode.
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 data63.0
Upgrade Firefox for Android to version 63 or later, which properly isolates favicon caching in private browsing mode. Until patched, avoid using private browsing mode on Firefox for Android or use alternative browsers.
Fix this in Firefox
Scoped from the published advisory
- Consultation2.0 h
- Implementation3.0 h
- Testing1.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-12400 — 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-2018-12400 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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