Description
Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, `resolvePartial()` in the Handlebars runtime resolves partial names via a plain property lookup on `options.partials` without guarding against prototype-chain traversal. When `Object.prototype` has been polluted with a string value whose key matches a partial reference in a template, the polluted string is used as the partial body and rendered without HTML escaping, resulting in reflected or stored XSS. Version 4.7.9 fixes the issue. Some workarounds are available. Apply `Object.freeze(Object.prototype)` early in application startup to prevent prototype pollution. Note: this may break other libraries, and/or use the Handlebars runtime-only build (`handlebars/runtime`), which does not compile templates and reduces the attack surface.
Problem types
CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Product status
References
github.com/...ars.js/security/advisories/GHSA-2qvq-rjwj-gvw9
github.com/...ommit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2
github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9