CVE-2020-6802Public exploitNetwork attack vector

Cross-site scripting via mismatched noscript parsing

Published Mar 24, 2020 · Updated Aug 4, 2024

Mutation XSS in Mozilla Bleach 3.1.0 and earlier allows remote attackers to execute JavaScript through sanitized HTML. BleachHTMLParser parses noscript content with scripting disabled, unlike JavaScript-enabled browsers, so a whitelisted raw tag mutates the output into executable markup. An application must pass attacker-controlled HTML to bleach.clean while allowing noscript and a raw-text tag, and a user must render the result in a browser.

CVSS severity6.1
Medium
EPSS probability1.73%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Mutation XSS in Mozilla Bleach 3.1.0 and earlier allows remote attackers to execute JavaScript through sanitized HTML. BleachHTMLParser parses noscript content with scripting disabled, unlike JavaScript-enabled browsers, so a whitelisted raw tag mutates the output into executable markup. An application must pass attacker-controlled HTML to bleach.clean while allowing noscript and a raw-text tag, and a user must render the result in a browser.

The record

CVE
CVE-2020-6802
Published
Mar 24, 2020
Updated
Aug 4, 2024
Vendor
Mozilla
Product
Bleach
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 24, 2020CVE 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=<=3.10

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Bleachversion=<=3.10

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/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')
T1059.007Command and Scripting Interpreter: JavaScript

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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