A flaw was found in the Quarkus Qute template engine. When the {#eval} section helper processes a sub-template, it fails to pass the parent template's content type information. This bypasses standard escaping mechanisms, allowing untrusted data to be output as raw, unescaped text. This vulnerability can lead to Cross-Site Scripting (XSS) and JSON Injection, potentially allowing a remote attacker to execute arbitrary code in a user's browser or manipulate data.
Users who cannot immediately upgrade can mitigate this issue by updating their templates to use the str:eval extension method instead of the {#eval} section helper.
Vulnerable pattern: {#eval snippet /}
Secure alternative: {str:eval(snippet)}