Cross-site scripting in bluemonday

MEDIUM 6.1CVE-2021-29272 · GHSA-3x58-xr87-2fcj · GO-2022-0762 · Published 27/03/2021 · updated 17/06/2026

In short

CVE-2021-29272 is a MEDIUM (CVSS 6.1) vulnerability affecting github.com/microcosm-cc/bluemonday, bluemonday (microco).
Chance of exploitation in the next 30 days (EPSS): 0.93%, higher than 60.6% of all vulnerabilities.
Fix: update to 1.0.5 or later.

Package	Affected versions	Patched versions
github.com/microcosm-cc/bluemonday Go	`< 1.0.5`	`1.0.5`
bluemonday microco	`< 1.0.5`	`1.0.5`

Description

bluemonday before 1.0.5 allows XSS because certain Go lowercasing converts an uppercase Cyrillic character, defeating a protection mechanism against the "script" string.

NVD description

bluemonday before 1.0.5 allows XSS because certain Go lowercasing converts an uppercase Cyrillic character, defeating a protection mechanism against the "script" string.

References

nvd.nist.gov/vuln/detail/CVE-2021-29272 · ADVISORY
microcosm-cc/bluemonday · WEB
microcosm-cc/bluemonday commit 524f142 · WEB
microcosm-cc/bluemonday · PACKAGE
microcosm-cc/bluemonday release v1.0.5 · WEB
pkg.go.dev/vuln/GO-2022-0762 · WEB
vuln.ryotak.me/advisories/4 · WEB
vuln.ryotak.me/advisories/4.txt · WEB

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Package

Affected versions

Patched versions

github.com/microcosm-cc/bluemonday

< 1.0.5

1.0.5

bluemonday

microco

< 1.0.5

1.0.5

Description

bluemonday before 1.0.5 allows XSS because certain Go lowercasing converts an uppercase Cyrillic character, defeating a protection mechanism against the "script" string.

NVD description

bluemonday before 1.0.5 allows XSS because certain Go lowercasing converts an uppercase Cyrillic character, defeating a protection mechanism against the "script" string.