CVE-2023-4053Public exploitNetwork attack vector

UI spoofing via foreground external protocol handler

Published Aug 1, 2023 · Updated Dec 18, 2025

UI spoofing in Mozilla Firefox before 116, Firefox ESR before 115.2, and Thunderbird before 115.2 allows remote attackers to mislead users. A crafted page enters fullscreen after launching a mailto URL, while the external mail program remains foregrounded and hides the browser's fullscreen notification. A user must click the page control and interact with the external handler; the attacker can then present deceptive fullscreen content without the expected warning.

CVSS severity6.5
Medium
EPSS probability0.77%
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 Mozilla Firefox before 116, Firefox ESR before 115.2, and Thunderbird before 115.2 allows remote attackers to mislead users. A crafted page enters fullscreen after launching a mailto URL, while the external mail program remains foregrounded and hides the browser's fullscreen notification. A user must click the page control and interact with the external handler; the attacker can then present deceptive fullscreen content without the expected warning.

The record

CVE
CVE-2023-4053
Published
Aug 1, 2023
Updated
Dec 18, 2025
Vendor
Mozilla
Product
Firefox
Classifications
CWE-59
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 1, 2023CVE publishedPublication date reported by the CVE source.
  2. Dec 18, 2025Record 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 <116

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <116
Mozilla · Thunderbirdversion=unspecified <115.2
Mozilla · Firefox ESRversion=unspecified <115.2

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/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 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 exploitPublished

Weakness, pattern, technique

CWE-59Improper Link Resolution Before File Access ('Link Following')

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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