CVE-2020-11888Public exploitNetwork attack vector

Cross-site scripting via incomplete-tag regex bypass

Published Apr 20, 2020 · Updated Aug 4, 2024

Cross-site scripting in python-markdown2 2.3.8 and earlier allows remote attackers to run script through crafted Markdown input. In safe_mode, _encode_incomplete_tags applies a regular expression that fails to recognize punctuation in element names, leaving event attributes unescaped. A consuming application must render attacker-controlled Markdown and a user must view the resulting HTML; script executes within the application's origin.

CVSS severity6.1
Medium
EPSS probability1.93%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in python-markdown2 2.3.8 and earlier allows remote attackers to run script through crafted Markdown input. In safe_mode, _encode_incomplete_tags applies a regular expression that fails to recognize punctuation in element names, leaving event attributes unescaped. A consuming application must render attacker-controlled Markdown and a user must view the resulting HTML; script executes within the application's origin.

The record

CVE
CVE-2020-11888
Published
Apr 20, 2020
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 20, 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?

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

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')
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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