FirefoxWeb browser · Mozilla
CVE-2023-6869
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 `<dialog>` element could have been manipulated to paint content outside of a sandboxed iframe. This could allow untrusted content to display under the guise of trusted content. This vulnerability affects Firefox < 121.
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 · moderate confidenceThe HTML `<dialog>` element in Firefox versions before 121 contains a flaw allowing content to be painted outside the boundaries of a sandboxed iframe. This enables UI redress attacks where malicious content can be layered over trusted content, potentially tricking users into interacting with unintended interface elements.
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
< 121.0CVSS 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
- 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 checksWork through these to decide whether this CVE applies to you.
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Check your Firefox browser versionOpen Firefox, click the menu button (three lines), select Help, then select About Firefox. The version number will be displayed.Affected if The version shown is below 121.0 (for example, 120.0, 120.0.1, etc.)
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Confirm the vulnerable feature is presentIn the Firefox address bar, type about:support and press Enter. Look for information about the browser build and configuration.Affected if Running any Firefox version prior to 121.0 regardless of configuration
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Identify if you use web applications with dialog elementsIf you are a web developer, audit your web applications for usage of the HTML <dialog> element by searching your codebase for <dialog> tags.Affected if You host web content using <dialog> elements that could be embedded in sandboxed iframes by malicious sites
You are affected if you run any Firefox version below 121.0 and either use or host web content containing HTML dialog elements.
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 · scoped121.0
Update Firefox to version 121 or later. As a defense-in-depth measure, web applications can implement X-Frame-Options: DENY or CSP frame-ancestors directives to control iframe embedding.
Firefox 121.0
- Open Firefox and navigate to Menu > Help > About Firefox to check for updates
- If an update is available, download and install Firefox 121.0 or later
- Alternatively, download Firefox 121.0 or later from the official Mozilla website and install over the existing version
- Restart Firefox after the update completes
- Verify the version by navigating to Menu > Help > About Firefox and confirming the version number is 121.0 or higher
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Firefox
Scoped from the published advisory
- Consultation2.0 h
- Implementation1.0 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 $1,456.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-6869 — 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-2023-6869 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
- No spam, self-promotion, credentials, or personal data