CVE-2026-4712

Private-window disclosure via inverted restoration flag

Published Mar 24, 2026 · Updated Mar 24, 2026

Information disclosure in Firefox and Thunderbird before 149 allows attackers to recover private-window information written to disk on macOS. HideWindowChrome recreates a Cocoa window by passing mWindow.restorable as the private-browsing flag instead of its inverse, turning private windows into restorable non-private windows. The leak requires macOS native fullscreen to be disabled; affected release and ESR builds then restore private windows as normal windows.

CVSS severity7.5
High
EPSS probability0.39%
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 and Thunderbird before 149 allows attackers to recover private-window information written to disk on macOS. HideWindowChrome recreates a Cocoa window by passing mWindow.restorable as the private-browsing flag instead of its inverse, turning private windows into restorable non-private windows. The leak requires macOS native fullscreen to be disabled; affected release and ESR builds then restore private windows as normal windows.

The record

CVE
CVE-2026-4712
Published
Mar 24, 2026
Updated
Mar 24, 2026
Vendor
Mozilla
Product
Firefox
Classifications
CWE-200
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Mar 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 24, 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 <149

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

Mozilla · Firefoxversion=unspecified <149
Mozilla · Thunderbirdversion=unspecified <140.9; version=unspecified <149
Mozilla · Firefox ESRversion=unspecified <140.9

Published CVSS scores

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-200Exposure of Sensitive Information to an Unauthorized Actor

Public exploit references

No public exploit references are available in this record.

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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