dbcve.org
FirefoxWeb browser · Mozilla

CVE-2016-5262

MEDIUM · 6.1 CVSS v3.0 Published 2016-08-05
Fix available
A fix is available. Upgrade to after 47.0.1 or later.
See remediation →
68/100
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
Mozilla Firefox before 48.0 and Firefox ESR 45.x before 45.3 process JavaScript event-handler attributes of a MARQUEE element within a sandboxed IFRAME element that lacks the sandbox="allow-scripts" attribute value, which makes it easier for remote attackers to conduct cross-site scripting (XSS) attacks via a crafted web site.

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

Mozilla Firefox before 48.0 and Firefox ESR 45.x before 45.3 contains a cross-site scripting (XSS) vulnerability where JavaScript event-handler attributes of a MARQUEE element can execute within a sandboxed IFRAME element that lacks the sandbox="allow-scripts" attribute. This allows attackers to bypass the intended sandbox restrictions and inject malicious scripts via crafted webpages.

MitigationUpgrade Firefox to version 48.0 or later (or ESR 45.3 or later) to apply the vendor patch. As a compensating control, implement Content Security Policy (CSP) headers to restrict inline script execution.

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:<= 47.0.1= 45.1.0= 45.1.1= 45.2.0= 45.3.0
LinuxOperating system
Affected:= 5.0= 6= 7

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
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.0/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 checks

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

  1. Identify installed Firefox version
    Open Firefox, go to Help > About Firefox (or navigate to about:support), or run 'firefox --version' from command line
    Affected if Version is 47.0.1 or lower, or is 45.1.0, 45.1.1, 45.2.0, or 45.3.0 (ESR 45.x before 45.3)
  2. Check for ESR version specifically
    In about:support, look for 'Version' field - ESR versions include 'ESR' in the version string (e.g., 45.3 (ESR)')
    Affected if Running Firefox ESR 45.x where x is less than 3 (45.0, 45.1, 45.2)
  3. Audit web pages for sandboxed IFRAME usage
    Search web application source code for '<iframe' elements containing 'sandbox' attribute, then check if 'allow-scripts' is absent from the sandbox value
    Affected if Sandboxed iframes exist without the 'allow-scripts' directive present
  4. Search for MARQUEE element usage in web content
    Inspect web application HTML for <marquee> tags, especially within IFRAME contexts or user-generated content areas
    Affected if MARQUEE elements with event-handler attributes (onstart, onfinish, onbounce, etc.) exist in content loaded within sandboxed iframes

You are affected if running Firefox 47.0.1 or earlier, or Firefox ESR 45.2 or earlier, and your web content contains MARQUEE elements with JavaScript event handlers inside sandboxed iframes that lack the allow-scripts attribute.

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 a release after 47.0.1
Interim mitigation

Upgrade Firefox to version 48.0 or later (or ESR 45.3 or later) to apply the vendor patch. As a compensating control, implement Content Security Policy (CSP) headers to restrict inline script execution.

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing1.0 h
  • Review / QA1.0 h
5.0 hours of engineering $890
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,424.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2016-5262 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2016-5262 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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