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FirefoxWeb browser · Mozilla

CVE-2023-4053

MEDIUM · 6.5 CVSS v3.1 Published 2023-08-01
Fix available
A fix is available. Upgrade to 116.0 or later.
See remediation →
72/100
Remediation priority · Elevated
Remotely reachable No privileges

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 · unedited
A website could have obscured the full screen notification by using a URL with a scheme handled by an external program, such as a mailto URL. This could have led to user confusion and possible spoofing attacks. This vulnerability affects Firefox < 116, Firefox ESR < 115.2, and Thunderbird < 115.2.

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 confidence

Firefox's full screen notification can be obscured by embedding a URL with an external scheme handler (e.g., mailto:) in the page, preventing users from seeing the notification that indicates a site has entered full screen mode. This enables UI spoofing where malicious sites can impersonate the browser or other sites.

MitigationUpgrade to Firefox 116+, Firefox ESR 115.2+, or Thunderbird 115.2+ to receive the security patch that prevents external URL schemes from obscuring the full screen notification.

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
Affected:< 116.0

CVSS 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
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/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 checks

Work through these to decide whether this CVE applies to you.

  1. Check installed Firefox version
    Navigate to Firefox menu > Help > About Firefox, or enter 'about:support' in the address bar, or run 'firefox --version' from command line
    Affected if The displayed version is any version prior to 116.0 (e.g., 115.x, 115.3, 115.0.1, etc.)
  2. Confirm Firefox edition and update source
    Check if this is standard Firefox, Firefox ESR, or Thunderbird by examining the application name in About dialog or package information
    Affected if Running Firefox (non-ESR) below 116.0, or if unable to confirm a patched version (116+) is available
  3. Verify full screen API behavior with external schemes
    Create a test HTML page with an anchor tag containing an external scheme (e.g., <a href="mailto:[email protected]">) and trigger full screen mode using the Fullscreen API while this element is present in the DOM
    Affected if The full screen notification prompt does not appear or is obscured when external scheme URLs are embedded in the page

A user is affected if their Firefox installation is version 115.x or lower, since the vulnerability allows malicious sites to hide the full screen notification using embedded external scheme URLs, enabling UI spoofing attacks.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Upgrade available Upgrade to 116.0 or later
Fixed in 116.0
Interim mitigation

Upgrade to Firefox 116+, Firefox ESR 115.2+, or Thunderbird 115.2+ to receive the security patch that prevents external URL schemes from obscuring the full screen notification.

Recommended fix High confidence

Firefox 116.0, Firefox ESR 115.2, or Thunderbird 115.2

  1. 1. Check current Firefox version by navigating to Help > About Firefox or running 'firefox --version' in terminal
  2. 2. Download and install Firefox 116.0 or later from www.mozilla.org
  3. 3. For enterprise/ESR users, upgrade to Firefox ESR 115.2 or later
  4. 4. Restart the browser after installation
  5. 5. Verify the version by checking Help > About Firefox confirms version 116.0 or higher
Caveat Routine browser update; no major breaking changes expected for typical users

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Firefox Scoped from the published advisory
  • Consultation8.0 h
  • Implementation40.0 h
  • Testing16.0 h
  • Review / QA8.0 h
72.0 hours of engineering $12,640
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $20,224.

Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-4053 in production — separate from our analysis above.

No notes yet

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What this is

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.

What belongs here
  • 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