CVE-2021-37700Public exploitNetwork attack vector

Browser script execution via unsanitized clipboard HTML

Published Aug 12, 2021 · Updated Aug 4, 2024

DOM-based XSS in GitHub paste-markdown before 0.3.4 allows remote attackers to execute JavaScript through crafted clipboard HTML. The generateText function assigns untrusted text/html clipboard content containing a table to a detached div's innerHTML without sanitization. Exploitation requires a user to copy attacker-controlled web content and paste it into an integrating page, exposing browser-accessible data.

CVSS severity6.5
Medium
EPSS probability1.66%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

DOM-based XSS in GitHub paste-markdown before 0.3.4 allows remote attackers to execute JavaScript through crafted clipboard HTML. The generateText function assigns untrusted text/html clipboard content containing a table to a detached div's innerHTML without sanitization. Exploitation requires a user to copy attacker-controlled web content and paste it into an integrating page, exposing browser-accessible data.

The record

CVE
CVE-2021-37700
Published
Aug 12, 2021
Updated
Aug 4, 2024
Vendor
Twitter
Product
paste-markdown
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 12, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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=< 0.3.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Twitter · paste-markdownversion=< 0.3.4

Published CVSS scores

6.5GitHub CNACVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/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.

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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')
T1059.007Command and Scripting Interpreter: JavaScript/JScript

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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