Handlebars.java provides logic-less and semantic Mustache templates with Java. Prior to 4.5.2, applications that pass user-controlled input to Handlebars.compile() using FileTemplateLoader or ClassPathTemplateLoader are vulnerable to path traversal, allowing arbitrary file read through template names derived from URL path parameters, request parameters, or other user-controlled sources. This issue is fixed in version 4.5.2.

handlebars.java FileTemplateLoader Path Traversal