FirefoxWeb browser · Mozilla
CVE-2020-6823
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 malicious extension could have called <code>browser.identity.launchWebAuthFlow</code>, controlling the redirect_uri, and through the Promise returned, obtain the Auth code and gain access to the user's account at the service provider. This vulnerability affects Firefox < 75.
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 vulnerability in Firefox < 75 allows malicious browser extensions to manipulate the redirect_uri parameter of the browser.identity.launchWebAuthFlow API. By controlling this parameter and intercepting the returned Promise, the extension can steal the OAuth authorization code and gain unauthorized access to the user's account at the service provider.
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
< 75.0CVSS 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
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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 Firefox versionOpen Firefox, click the menu (three lines) > Help > About Firefox, or visit about:support, or run 'firefox --version' from command lineAffected if The displayed version is below 75.0 (for example 74.0, 73.0, etc.)
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Identify extensions using OAuth identity APIReview installed browser extensions and their manifest.json files for the 'identity' permission and use of browser.identity.launchWebAuthFlow API in their codeAffected if Any extension with the 'identity' permission is installed and uses the launchWebAuthFlow method for OAuth flows
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Check for OAuth redirect handlingExamine how extensions handle the redirect_uri parameter in their OAuth implementation - look for code that processes or modifies the redirect URL passed to launchWebAuthFlowAffected if The extension code does not validate that redirect_uri matches the expected value after the API call completes
You are affected if your Firefox version is below 75.0 AND you have browser extensions using the identity API for OAuth authentication.
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 · scoped75.0
Upgrade Firefox to version 75 or later. Alternatively, if upgrading is not feasible, restrict or audit browser extension permissions and implement additional validation of OAuth redirect URIs at the service provider side.
Firefox 75.0 or later
- Upgrade Firefox to version 75.0 or later
- Verify the upgrade by checking Help > About Firefox to confirm the installed version
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Firefox
Scoped from the published advisory
- Consultation8.0 h
- Implementation16.0 h
- Testing8.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $10,240.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-6823 — 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-2020-6823 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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