CVE-2021-39175: XSS vector in slide mode speaker-view

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-08-30 · updated 2026-06-17
Weakness: CWE-74

Description

HedgeDoc is a platform to write and share markdown. In versions prior to 1.9.0, an unauthenticated attacker can inject arbitrary JavaScript into the speaker-notes of the slide-mode feature by embedding an iframe hosting the malicious code into the slides or by embedding the HedgeDoc instance into another page. The problem is patched in version 1.9.0. There are no known workarounds aside from upgrading.

Affected products

hedgedoc: before 1.9.0 — fixed in 1.9.0

How to fix

Upgrade to a fixed version: hedgedoc 1.9.0. Check the vendor advisory for mitigations.

References

https://github.com/hedgedoc/hedgedoc/pull/1369
https://github.com/hedgedoc/hedgedoc/pull/1375
https://github.com/hedgedoc/hedgedoc/pull/1513
https://github.com/hedgedoc/hedgedoc/security/advisories/GHSA-j748-779h-9697
https://github.com/hedgedoc/hedgedoc/pull/1369
https://github.com/hedgedoc/hedgedoc/pull/1375
https://github.com/hedgedoc/hedgedoc/pull/1513
https://github.com/hedgedoc/hedgedoc/security/advisories/GHSA-j748-779h-9697

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