Ubuntu LinuxOperating system · Canonical
CVE-2018-5176
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 · uneditedThe JSON Viewer displays clickable hyperlinks for strings that are parseable as URLs, including "javascript:" links. If a JSON file contains malicious JavaScript script embedded as "javascript:" links, users may be tricked into clicking and running this code in the context of the JSON Viewer. This can allow for the theft of cookies and authorization tokens which are accessible to that context. This vulnerability affects Firefox < 60.
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 built-in JSON Viewer creates clickable hyperlinks from URL-like strings in JSON data without filtering dangerous protocols like 'javascript:'. When users view malicious JSON files containing javascript: links, clicking them executes the embedded script in the JSON Viewer's origin context, allowing theft of cookies and authorization tokens.
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
Ubuntu LinuxOperating system
= 14.04= 16.04= 17.10= 18.04
FirefoxWeb browser
< 60.0CVSS 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:3.0/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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Confirm Firefox is installedCheck for Firefox installation by running 'which firefox' or looking in common installation paths like /usr/bin/firefox, ~/.mozilla/firefox, or on Windows in Program FilesAffected if Firefox is not installed on the system
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Determine installed Firefox versionRun 'firefox --version' or 'firefox -v' in terminal, or access Firefox menu > Help > About FirefoxAffected if The displayed version number is less than 60.0 (for example 59.x, 58.x, etc.)
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Identify the JSON Viewer usage contextThe JSON Viewer is a built-in Firefox feature that activates when opening .json files directly in the browser. Check if users open JSON files in Firefox by examining file associations or recent file openingsAffected if Users routinely open JSON files directly in Firefox using the built-in JSON viewer
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Verify javascript: URL execution contextThis is a built-in behavior in affected versions - no specific configuration to check. The vulnerability exists whenever JSON Viewer displays URL-like stringsAffected if Firefox version is below 60.0 and users view JSON files with clickable links in the browser
Your environment is affected if Firefox version is below 60.0 and users view JSON files using Firefox's built-in JSON Viewer feature, as the javascript: protocol filtering is missing in vulnerable versions.
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 data60.0
Upgrade Firefox to version 60 or later, which includes the fix that filters out javascript: URLs in the JSON Viewer. Avoid clicking untrusted links in JSON files.
Fix this in Ubuntu Linux
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-2018-5176 — 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-2018-5176 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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