CVE intelligence and bounded remediation

CVE-2020-26211 — Bookstackapp Bookstack security vulnerability

High CVSS 8.7

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.

Severity
High
CVSS
8.7 (3.1)
Published
2020-11-03
CISA KEV
Not currently listed
Ecosystem
javascript/npm
Weaknesses
CWE-79

Affected products

  • bookstackapp / bookstack

Matched remediation archetype

Cross-site scripting and unsafe browser output

This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.

Check exposure

  • Trace reflected, stored, and DOM-derived untrusted values into HTML, attributes, URLs, styles, scripts, and client-side template sinks.
  • Identify affected origins, authenticated user roles, sensitive browser capabilities, and where content is shared across tenants.
  • Review framework escaping, rich-text sanitization, legacy templates, and client-side rendering paths.

Remediate safely

  • Use context-aware framework output encoding and safe DOM APIs; keep untrusted data out of executable contexts.
  • Sanitize intentionally supported markup with a maintained allowlist policy and validate URLs and attributes separately.
  • Update affected rendering components and add tests for every output context using inert sentinel markup.

Authoritative sources

Complete CVE record and remediation plan

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