FirefoxWeb browser · Mozilla
CVE-2016-9071
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 · uneditedContent Security Policy combined with HTTP to HTTPS redirection can be used by malicious server to verify whether a known site is within a user's browser history. This vulnerability affects Firefox < 50.
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 history sniffing vulnerability in Firefox allows malicious servers to detect whether a user has visited specific sites by abusing Content Security Policy (CSP) combined with HTTP to HTTPS redirection. The attack exploits how browsers handle CSP directives during redirection to infer visitor history.
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
< 50.0CVSS 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
- Low
- Integrity
- None
- Availability
- None
CVSS:3.0/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 checksWork through these to decide whether this CVE applies to you.
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Determine installed Firefox versionOpen Firefox, go to Help > About Firefox, or run 'firefox --version' from command lineAffected if The displayed version is below 50.0 (e.g., 49.x, 48.x, etc.)
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Confirm CSP processing during HTTP to HTTPS redirectsThis is handled internally by the browser and cannot be directly inspected. The vulnerability exists in how Firefox processes CSP directives when a redirect from HTTP to HTTPS occurs.Affected if Firefox version is below 50.0 and the browser processes CSP headers during redirection (default behavior in affected versions)
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Check if browsing history could be exposedThis is a passive attack that runs when visiting a malicious server. The attacker can detect whether specific URLs were visited by observing how the browser handles CSP policy decisions during HTTP to HTTPS redirects.Affected if User runs Firefox below 50.0 and visits a malicious website that implements the CSP history sniffing technique
A user is affected if they are running any version of Mozilla Firefox below 50.0, as the vulnerability is a version-specific flaw in how the browser handles CSP directives during HTTP to HTTPS redirection.
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 data50.0
Upgrade Firefox to version 50 or later, which contains the fix for this CSP-based history sniffing vulnerability.
Fix this in Firefox
Scoped from the published advisory
- Consultation1.0 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 $1,200.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2016-9071 — 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-2016-9071 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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