CVE-2021-24000Public exploitNetwork attack vector

File disclosure via cross-tab pointer-lock race

Published Jun 24, 2021 · Updated Aug 3, 2024

Cross-tab clickjacking in Mozilla Firefox before 88 allows remote attackers to disclose selected local files through crafted web content. A setTimeout-timed requestPointerLock() race leaves pointer lock and mouse events bound to the attacker’s tab after window.open() makes a different tab visible. A user must open the crafted page and click what appears to be a file control on the visible site; the hidden origin receives the selected file.

CVSS severity3.1
Low
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

Cross-tab clickjacking in Mozilla Firefox before 88 allows remote attackers to disclose selected local files through crafted web content. A setTimeout-timed requestPointerLock() race leaves pointer lock and mouse events bound to the attacker’s tab after window.open() makes a different tab visible. A user must open the crafted page and click what appears to be a file control on the visible site; the hidden origin receives the selected file.

The record

CVE
CVE-2021-24000
Published
Jun 24, 2021
Updated
Aug 3, 2024
Vendor
Mozilla
Product
Firefox
Classifications
CWE-362
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 24, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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 <88

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <88

Published CVSS scores

3.1NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N
2.6NIST NVDAV:N/AC:H/Au:N/C:P/I:N/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

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

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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