CVE intelligence and bounded remediation

CVE-2021-28002 — Textpattern Textpattern security vulnerability

Medium CVSS 5.4

A persistent cross-site scripting vulnerability was discovered in the Excerpt parameter in Textpattern CMS 4.9.0 which allows remote attackers to execute arbitrary code via a crafted payload entered into the URL field. The vulnerability is triggered by users visiting the 'Articles' page.

Severity
Medium
CVSS
5.4 (3.1)
Published
2021-08-19
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-79

Affected products

  • textpattern / textpattern / 4.9.0

Matched remediation archetype

Cross-site scripting and unsafe browser output

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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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