Affected versions of marked are susceptible to a cross-site scripting vulnerability in link components when sanitize:true is configured.

Proof of Concept

This flaw exists because link URIs containing HTML entities get processed in an abnormal manner. Any HTML Entities get parsed on a best-effort basis and included in the resulting link, while if that parsing fails that character is omitted.

For example:

A link URI such as javascript&#x58document;alert(1) Renders a valid link that when clicked will execute alert(1).

Recommendation

Update to version 0.3.6 or later.