CVE-2023-6208Public exploitNetwork attack vector

Clipboard poisoning via ungated Selection API autocopy

Published Nov 21, 2023 · Updated Feb 13, 2025

Clipboard poisoning in Firefox before 120, Firefox ESR before 115.5.0, and Mozilla Thunderbird before 115.5 lets remote attackers alter X11 data. AutoCopyListener treats Selection.selectAllChildren() calls from page JavaScript as select-all events and copies the selected text into the X11 primary selection without a secure context, permission, or user activation. Exposure requires an X11 session and a later paste from the primary selection; Thunderbird also requires a browser-like context because message scripting is disabled.

CVSS severity8.8
High
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

Clipboard poisoning in Firefox before 120, Firefox ESR before 115.5.0, and Mozilla Thunderbird before 115.5 lets remote attackers alter X11 data. AutoCopyListener treats Selection.selectAllChildren() calls from page JavaScript as select-all events and copies the selected text into the X11 primary selection without a secure context, permission, or user activation. Exposure requires an X11 session and a later paste from the primary selection; Thunderbird also requires a browser-like context because message scripting is disabled.

The record

CVE
CVE-2023-6208
Published
Nov 21, 2023
Updated
Feb 13, 2025
Vendor
Mozilla
Product
Firefox
Classifications
T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 21, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 13, 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 <120

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <120
Mozilla · Thunderbirdversion=unspecified <115.5
Mozilla · Firefox ESRversion=unspecified <115.5.0

Published CVSS scores

8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

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

T1203Exploitation for Client Execution

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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