FirefoxWeb browser · Mozilla
CVE-2023-23603
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 · uneditedRegular expressions used to filter out forbidden properties and values from style directives in calls to `console.log` weren't accounting for external URLs. Data could then be potentially exfiltrated from the browser. This vulnerability affects Firefox < 109, Firefox ESR < 102.7, and Thunderbird < 102.7.
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 regex-based filter for style directives in console.log failed to properly sanitize external URLs, potentially allowing malicious websites to exfiltrate sensitive data from the browser through manipulated style attributes.
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
< 109.0
Firefox EsrWeb browser
< 102.7< 102.7CVSS 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
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/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.
-
Check Firefox versionNavigate to Menu > Help > About Firefox, or enter 'about:support' in the address bar to view the version number under Application BasicsAffected if Version is below 109.0 (regular Firefox)
-
Check Firefox ESR versionNavigate to Menu > Help > About Firefox, or enter 'about:support' in the address bar. ESR versions display 'ESR' in the version stringAffected if Version is below 102.7 (Firefox ESR)
-
Check Thunderbird versionNavigate to Menu > Help > About Thunderbird, or enter 'about:support' in the address bar to view the version numberAffected if Version is below 102.7 (Thunderbird)
A user is affected if they have Firefox below 109.0, Firefox ESR below 102.7, or Thunderbird below 102.7 installed and use the browser to view untrusted web content that could manipulate console.log style directives.
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 · scoped102.7109.0
Upgrade Firefox to version 109 or later, Firefox ESR to 102.7 or later, or Thunderbird to 102.7 or later to apply the patched regex handling for URL-based style directives.
Firefox 109.0, Firefox ESR 102.7, or Thunderbird 102.7
- 1. Check the current version of Firefox, Firefox ESR, or Thunderbird by navigating to the application's Help menu and selecting 'About'
- 2. For Firefox: Open the application, go to Menu > Help > About Firefox, and click 'Check for Updates' to automatically update to 109.0 or later
- 3. For Firefox ESR: Open the application, go to Menu > Help > About Firefox, and click 'Check for Updates' to automatically update to 102.7 or later
- 4. For Thunderbird: Open the application, go to Menu > Help > About Thunderbird, and click 'Check for Updates' to automatically update to 102.7 or later
- 5. Alternatively, download the latest version directly from the official Mozilla website (www.mozilla.org) and reinstall
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Firefox
Scoped from the published advisory
- Consultation2.0 h
- Implementation3.0 h
- Testing1.0 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 $2,032.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-23603 — 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-2023-23603 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
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