CVE-2021-37518Public exploitNetwork attack vector

Arbitrary script execution via guessable omnibar token

Published Feb 3, 2023 · Updated Mar 26, 2025

Universal cross-site scripting in Vimium Extension 1.66 and earlier allows remote attackers to run arbitrary JavaScript via the omnibar. The extension uses a low-entropy, site-spanning secret token to authenticate messages between content scripts, allowing a malicious page to guess the token and send invalid omnibar messages. A victim must visit the attacker's page and interact with it; successful exploitation runs script in the extension context across other sites.

CVSS severity6.1
Medium
EPSS probability0.68%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Universal cross-site scripting in Vimium Extension 1.66 and earlier allows remote attackers to run arbitrary JavaScript via the omnibar. The extension uses a low-entropy, site-spanning secret token to authenticate messages between content scripts, allowing a malicious page to guess the token and send invalid omnibar messages. A victim must visit the attacker's page and interact with it; successful exploitation runs script in the extension context across other sites.

The record

CVE
CVE-2021-37518
Published
Feb 3, 2023
Updated
Mar 26, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 3, 2023CVE publishedPublication date reported by the CVE source.
  2. Mar 26, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.1CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
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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