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FirefoxWeb browser · Mozilla

CVE-2019-11720

MEDIUM · 6.1 CVSS v3.1 Published 2019-07-23
Fix available
A fix is available. Upgrade to 68.0 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
Some unicode characters are incorrectly treated as whitespace during the parsing of web content instead of triggering parsing errors. This allows malicious code to then be processed, evading cross-site scripting (XSS) filtering. This vulnerability affects Firefox < 68.

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

In Firefox versions before 68, certain unicode characters are incorrectly parsed as whitespace instead of triggering errors. Attackers can inject these characters into web content to bypass XSS filters, as the malicious code gets processed after the unicode whitespace is normalized/ignored during parsing.

MitigationUpgrade Firefox to version 68 or later to receive the security patch that properly validates unicode characters as non-whitespace.

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:< 68.0
LeapOperating system
Affected:= 15.0= 15.1

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:3.1/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. Check installed Firefox version
    Open Firefox, go to Help > About Firefox, or type 'about:support' in the address bar, or run 'firefox --version' from command line
    Affected if Version displayed is earlier than 68.0 (e.g., 67.x, 66.x, etc.)
  2. Verify Firefox version on Opensuse Leap
    If using Opensuse Leap 15.0 or 15.1, run 'rpm -qa | grep firefox' or check via YaST > Software Management to see the installed Firefox package version
    Affected if Opensuse Leap 15.0 or 15.1 is running with any Firefox version below 68.0
  3. Confirm unicode whitespace behavior
    Create a test HTML file containing unicode whitespace characters (U+200B zero-width space, U+3000 ideographic space) and attempt to parse the HTML in the browser to verify if they are incorrectly treated as valid whitespace
    Affected if These unicode characters are accepted without triggering parsing errors (indicating the vulnerability is present)

You are affected if your installed Firefox version is below 68.0, or if you are running Opensuse Leap 15.0/15.1 with a bundled Firefox version below 68.0.

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 68.0 or later
Fixed in 68.0
Interim mitigation

Upgrade Firefox to version 68 or later to receive the security patch that properly validates unicode characters as non-whitespace.

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.

Scan for this in your stack

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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-2019-11720 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