CVE-2026-66829
URL Redirection to Untrusted Site ('Open Redirect') vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows a remote attacker to force visitors of a page to navigate to a site of the attacker's choosing via a <meta http-equiv="refresh"> element in sanitized HTML. HtmlSanitizeEx.html5/1 keeps attacker-supplied <meta> elements in its output. A meta element acts on the whole document rather than on the fragment it was embedded in, so it can also declare document-wide directives such as Content-Security-Policy. This is not cross-site scripting. Browsers do not navigate a meta refresh to a javascript: URL, so the uppercase JAVASCRIPT: filter bypass yields no script execution and none was demonstrated. This issue affects html_sanitize_ex: from 0.3.1 before 1.5.3.
- Affected products
- Html Sanitize Ex
- Rrrene Htmlsanitizeex
- < 1.5.3
- CVSS 3.1
- 6.1 MEDIUM
- EPSS
- 0.5% (40th percentile)
- Weakness
- CWE-601
- NVD status
- Analyzed
- Published
- 2026-08-06
- Attack patterns
- CAPEC-154
Workaround
Sanitize with basic_html/1, markdown_html/1 or strip_tags/1, none of which allow meta, or define a custom scrubber that omits it.
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