CVE-2026-0888Public exploitNetwork attack vector

Locale fingerprinting via XML pretty-print measurements

Published Jan 13, 2026 · Updated Jan 13, 2026

Information disclosure in Firefox before 147 allows remote attackers to fingerprint browser locale through crafted XML content. Firefox XMLPrettyPrinter localizes its introductory text even when English-language spoofing is enabled, so scripts can bucket its rendered height through narrow iframes. Exploitation requires processing attacker-controlled XML, and the result is indirect disclosure of locale and rendering-environment characteristics rather than document data.

CVSS severity5.3
Medium
EPSS probability0.35%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in Firefox before 147 allows remote attackers to fingerprint browser locale through crafted XML content. Firefox XMLPrettyPrinter localizes its introductory text even when English-language spoofing is enabled, so scripts can bucket its rendered height through narrow iframes. Exploitation requires processing attacker-controlled XML, and the result is indirect disclosure of locale and rendering-environment characteristics rather than document data.

The record

CVE
CVE-2026-0888
Published
Jan 13, 2026
Updated
Jan 13, 2026
Vendor
Mozilla
Product
Firefox
Classifications
CWE-200, T1592.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 13, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 13, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <147

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <147

Published CVSS scores

5.3CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-200Exposure of Sensitive Information to an Unauthorized Actor
T1592.004Gather Victim Host Information: Client Configurations

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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