CVE-2020-26211: Cross-Site Scripting in BookStack

Severity: high (CVSS 8.7 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-11-03 · updated 2026-06-17
Weakness: CWE-79

Description

In BookStack before version 0.30.4, a user with permissions to edit a page could insert JavaScript code through the use of `javascript:` URIs within a link or form which would run, within the context of the current page, when clicked or submitted. Additionally, a user with permissions to edit a page could insert a particular meta tag which could be used to silently redirect users to a alternative location upon visit of a page. Dangerous content may remain in the database but will be removed before being displayed on a page. If you think this could have been exploited the linked advisory provides a SQL query to test. As a workaround without upgrading, page edit permissions could be limited to only those that are trusted until you can upgrade although this will not address existing exploitation of this vulnerability. The issue is fixed in BookStack version 0.30.4.

Affected products

bookstackapp/bookstack: before 0.30.4 — fixed in 0.30.4

How to fix

Upgrade to a fixed version: bookstackapp/bookstack 0.30.4. Check the vendor advisory for mitigations.

References

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