FirefoxWeb browser · Mozilla
CVE-2020-26962
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 · uneditedCross-origin iframes that contained a login form could have been recognized by the login autofill service, and populated. This could have been used in clickjacking attacks, as well as be read across partitions in dynamic first party isolation. This vulnerability affects Firefox < 83.
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 confidenceFirefox's login autofill service incorrectly populated credentials in cross-origin iframes containing login forms. This allowed attackers to exploit clickjacking techniques by embedding invisible login forms from other origins and tricking the browser into autofilling stored credentials, which could then be exfiltrated.
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
< 83.0CVSS 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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Check Firefox versionOpen Firefox, click the menu button (three horizontal lines), then click Help > About Firefox. The version number is displayed on this page.Affected if The displayed version is less than 83.0 (for example, 82.0, 82.0.1, etc.)
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Verify password autofill is enabledGo to Firefox Preferences > Privacy & Security > Logins and Passwords. Check if 'Ask to save logins and passwords for websites' is enabled.Affected if Autofill is enabled and Firefox version is below 83.0 - stored credentials could be exfiltrated via iframe clickjacking
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Confirm saved logins existIn the same Logins and Passwords settings, click 'Saved Logins' to view stored credentials.Affected if There are saved logins stored in Firefox and the version is below 83.0, making credential theft possible
A user is affected if they are running any Firefox version below 83.0 with password autofill enabled and stored credentials present in 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.
From vendor data83.0
Upgrade Firefox to version 83 or later. Additionally, web applications can set X-Frame-Options: DENY or Content-Security-Policy: frame-ancestors to prevent their login pages from being embedded in iframes.
Fix this in Firefox
Scoped from the published advisory
- Consultation1.0 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 $1,200.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-26962 — 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-2020-26962 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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