CVE-2023-6869Public exploitNetwork attack vector

Content spoofing via sandboxed iframe paint escape

Published Dec 19, 2023 · Updated May 7, 2025

UI spoofing in Mozilla Firefox before 121 allows remote attackers to display untrusted content as trusted content through a crafted webpage. A modal dialog containing fixed-position content inside a transformed, sandboxed iframe is painted beyond the iframe because subdocument display items are flattened without preserving the clip. A user must load content embedding the crafted frame; painted overflow does not receive hit-testing, limiting the reported effect to visual deception.

CVSS severity6.5
Medium
EPSS probability0.56%
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 121 allows remote attackers to display untrusted content as trusted content through a crafted webpage. A modal dialog containing fixed-position content inside a transformed, sandboxed iframe is painted beyond the iframe because subdocument display items are flattened without preserving the clip. A user must load content embedding the crafted frame; painted overflow does not receive hit-testing, limiting the reported effect to visual deception.

The record

CVE
CVE-2023-6869
Published
Dec 19, 2023
Updated
May 7, 2025
Vendor
Mozilla
Product
Firefox
Classifications
T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 19, 2023CVE publishedPublication date reported by the CVE source.
  2. May 7, 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 <121

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <121

Published CVSS scores

6.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
6.5NISTCVSS: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.

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 exploitPublished

Weakness, pattern, technique

T1189Drive-by Compromise

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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