Clipboard overwrite via reload-carried user activation
Published Sep 17, 2024 · Updated Mar 18, 2025
Clipboard bypass in Firefox before 129, ESR before 128.3, and Thunderbird before 128.3 allows remote attackers to overwrite clipboard data. A user-triggered reload carries transient activation into the new document, where a beforeunload handler writes attacker-controlled text without the expected prompt. A victim must navigate or reload an attacker-controlled page while activation remains valid; the write can replace clipboard contents but cannot read them.
Summary
What happened
Clipboard bypass in Firefox before 129, ESR before 128.3, and Thunderbird before 128.3 allows remote attackers to overwrite clipboard data. A user-triggered reload carries transient activation into the new document, where a beforeunload handler writes attacker-controlled text without the expected prompt. A victim must navigate or reload an attacker-controlled page while activation remains valid; the write can replace clipboard contents but cannot read them.
The record
- CVE
- CVE-2024-8900
- Published
- Sep 17, 2024
- Updated
- Mar 18, 2025
- Vendor
- Mozilla
- Product
- Firefox
- Classifications
- CWE-732
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 17, 2024CVE publishedPublication date reported by the CVE source.
- Mar 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.
- Affected versionversion=unspecified <129
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
- Mozilla Bugzilla minimal clipboard-write testcaseproof of concept · demonstrated
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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