CVE-2026-33916 Handlebars.js has Prototype Pollution Leading to XSS through Partial Template Injection

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...

CVE-2026-33916

Handlebars.js CVE-2026-33916 affects 4.0.0–4.7.8 where resolvePartial() looks up partials via options.partials without guarding prototype traversal. If Object.prototype is polluted with a string key matching a partial, that string becomes the partial body and is rendered unescaped, enabling refle...