FirefoxWeb browser · Mozilla
CVE-2021-43530
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 · uneditedA Universal XSS vulnerability was present in Firefox for Android resulting from improper sanitization when processing a URL scanned from a QR code. *This bug only affects Firefox for Android. Other operating systems are unaffected.*. This vulnerability affects Firefox < 94.
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 confidenceA Universal XSS (UXSS) vulnerability in Firefox for Android allows script execution through malicious URLs scanned from QR codes due to improper input sanitization. This client-side browser flaw enables attacks within the browser context, affecting only Firefox versions prior to 94 on Android devices.
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
< 94.0CVSS 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
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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 device settings under Apps > Firefox. Verify the package name is 'org.mozilla.firefox' (not Firefox Focus or Firefox Preview). This vulnerability only affects the main Firefox for Android application.Affected if Any other Firefox variant (Focus, Preview, Firefox Lite) is installed - those are NOT affected by this specific CVE.
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Check installed Firefox versionOpen Firefox for Android, tap the three-dot menu, go to Settings > About Firefox. Note the version number displayed.Affected if Version displayed is lower than 94.0 (for example, 93.x, 92.x, etc.). Versions 94.0 and later are patched.
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Verify QR code scanning usageDetermine if the Firefox for Android QR code scanner feature is used. This is typically accessible via the address bar scan icon or the app's scanning functionality.Affected if QR code scanning feature has been used to scan URLs from external sources. The vulnerability is triggered when processing malicious URLs from QR codes.
User is affected if Firefox for Android (org.mozilla.firefox) version is below 94.0 AND QR code URLs have been scanned with the browser.
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 · scoped94.0
Update Firefox for Android to version 94 or later to patch the sanitization vulnerability in QR code URL processing.
Firefox 94.0 for Android
- Verify the current Firefox for Android version by navigating to Settings > Firefox
- Navigate to the Google Play Store and search for Firefox
- Update Firefox for Android to version 94.0 or later
- Restart the application after the update completes
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-2021-43530 — 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-2021-43530 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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