FirefoxWeb browser · Mozilla
CVE-2017-7834
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 "data:" URL loaded in a new tab did not inherit the Content Security Policy (CSP) of the original page, allowing for bypasses of the policy including the execution of JavaScript. In prior versions when "data:" documents also inherited the context of the original page this would allow for potential cross-site scripting (XSS) attacks. This vulnerability affects Firefox < 57.
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 versions before 57 contained a vulnerability where 'data:' URLs loaded in new tabs did not inherit the Content Security Policy from the original page, allowing attackers to bypass CSP protections and potentially execute arbitrary JavaScript (XSS).
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
<= 56.0.2CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Check installed Firefox versionOpen Firefox, go to Help > About Firefox, or run 'firefox --version' from command lineAffected if Version displayed is 56.0.2 or lower (any version before 57.0)
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Verify if Content Security Policy is in useInspect web application headers for 'Content-Security-Policy' response header, or check browser extensions that manage CSP policiesAffected if CSP policies are actively defined and enforced on web applications accessed through the browser
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Determine if data: URLs are opened in new tabsReview browser usage patterns or web application behavior that loads data: URLs (such as data: URIs for images, scripts, or HTML content) in new browser tabsAffected if Users or applications load data: URLs in newly opened tabs while CSP is intended to protect those resources
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Confirm data: URL inheritance behaviorOpen a page with CSP, then open a data: URL in a new tab via link or script, then inspect the new tab's security information (page info) to verify if CSP headers are presentAffected if The data: URL in the new tab does not inherit or display the CSP from the originating page (CSP appears missing or different)
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Review browser configuration for data: URL handlingEnter 'about:config' in address bar and search for 'security.data_uri.attributes' or similar data: URI related settingsAffected if Default settings allow data: URIs to load without inheriting parent page security policies
Environment is affected if Firefox version is 56.0.2 or lower and data: URLs can be loaded in new tabs without inheriting Content Security Policy from the originating page.
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 dataUpgrade Firefox to version 57 or later. Organizations should ensure all instances of vulnerable Firefox versions are updated to remediate this CSP bypass vulnerability.
Fix this in Firefox
Scoped from the published advisory
- Consultation1.0 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-2017-7834 — 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-2017-7834 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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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.
- 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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