CVE intelligence and bounded remediation

CVE-2020-13959 — The default error page for VelocityView in Apache Velocity Tools prior to 3.1 reflects back the vm file that was entered as part of the URL

Medium CVSS 6.1

The default error page for VelocityView in Apache Velocity Tools prior to 3.1 reflects back the vm file that was entered as part of the URL. An attacker can set an XSS payload file as this vm file in the URL which results in this payload being executed. XSS vulnerabilities allow attackers to execute arbitrary JavaScript in the context of the attacked website and the attacked user. This can be abused to steal session cookies, perform requests in the name of the victim or for phishing attacks.

Severity
Medium
CVSS
6.1 (3.1)
Published
2021-03-10
CISA KEV
Not currently listed
Ecosystem
javascript/npm
Weaknesses
CWE-79

Affected products

  • apache / velocity_tools
  • debian / debian_linux / 9.0

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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