Wiki.js is al wiki app built on Node.js. Client side template injection was discovered, that could allow an attacker to inject malicious JavaScript into the content section of pages that would execute once a victim loads the page that contains the payload. This was possible through the injection of a invalid HTML tag with a template injection payload on the next line. This vulnerability is fixed in 2.5.303.
The product uses a template engine to insert or process externally-influenced input, but it does not neutralize or incorrectly neutralizes special elements or syntax that can be interpreted as template expressions or other code directives when processed by the engine.