CVE-2023-5726Network attack vector

UI spoofing via file-picker focus failure

Published Oct 24, 2023 · Updated Sep 11, 2024

UI spoofing in Firefox before 119, Firefox ESR before 115.4, and Thunderbird before 115.4.1 allows remote attackers to hide fullscreen warnings. The macOS Cocoa widget fails to send the expected deactivate event when a modal file-open dialog appears, so web content does not receive the blur event needed to preserve the fullscreen warning. Exploitation requires a macOS user to visit a crafted site, enter fullscreen, and open its file picker, enabling address-bar spoofing without code execution or service interruption.

CVSS severity4.3
Medium
EPSS probability0.60%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

UI spoofing in Firefox before 119, Firefox ESR before 115.4, and Thunderbird before 115.4.1 allows remote attackers to hide fullscreen warnings. The macOS Cocoa widget fails to send the expected deactivate event when a modal file-open dialog appears, so web content does not receive the blur event needed to preserve the fullscreen warning. Exploitation requires a macOS user to visit a crafted site, enter fullscreen, and open its file picker, enabling address-bar spoofing without code execution or service interruption.

The record

CVE
CVE-2023-5726
Published
Oct 24, 2023
Updated
Sep 11, 2024
Vendor
Mozilla
Product
Firefox
Classifications
Unavailable
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 24, 2023CVE publishedPublication date reported by the CVE source.
  2. Sep 11, 2024Record 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 <119

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <119
Mozilla · Thunderbirdversion=unspecified <115.4.1
Mozilla · Firefox ESRversion=unspecified <115.4

Published CVSS scores

4.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

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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