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FirefoxWeb browser · Mozilla

CVE-2020-15680

MEDIUM · 5.3 CVSS v3.1 Published 2020-10-22
Fix available
A fix is available. Upgrade to 82.0 or later.
See remediation →
62/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

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
If a valid external protocol handler was referenced in an image tag, the resulting broken image size could be distinguished from a broken image size of a non-existent protocol handler. This allowed an attacker to successfully probe whether an external protocol handler was registered. This vulnerability affects Firefox < 82.

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 versions before 82 contained a vulnerability where the broken image size differed depending on whether an external protocol handler (like 'skype:' or 'spotify:') was valid versus non-existent. This size difference allowed attackers to enumerate which protocol handlers are registered on a user's system, revealing installed applications.

MitigationUpdate Firefox to version 82 or later. No application-side code changes are required as this is a browser vulnerability.

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:< 82.0

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
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

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

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

  1. Check Firefox version
    Open Firefox, click the menu button (three horizontal lines), select Help, then select About Firefox. The version number will be displayed.
    Affected if Version is below 82.0 (for example, 81.x, 80.x, etc.)
  2. Verify the vulnerability condition
    This vulnerability exists in Firefox's image rendering when handling external protocol handlers (such as skype: or spotify:) in broken image scenarios. No special configuration toggle exists - it is present by default in affected versions.
    Affected if Firefox version is below 82.0 and the browser is used to load content that could contain external protocol handler references

You are affected if you are running any Mozilla Firefox version prior to 82.0 on your system.

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.

From vendor data
Upgrade available Upgrade to 82.0 or later
Fixed in 82.0
Interim mitigation

Update Firefox to version 82 or later. No application-side code changes are required as this is a browser vulnerability.

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
1.0 hours of engineering $750
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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-2020-15680 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