https://vulnerability.circl.lu Contains only the most 10 recent entries. http://www.rssboard.org/rss-specification python-feedgen en Mon, 05 Oct 2026 08:29:01 +0000 https://vulnerability.circl.lu/vuln/ghsa-2qvq-rjwj-gvw9 <p><strong>Affected:</strong> npm: handlebars</p> <p>## Summary</p> <p>`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.</p> <p>## Description</p> <p>The root cause is in `lib/handlebars/runtime.js` inside `resolvePartial()` and `invokePartial()`:</p> <p>```javascript // Vulnerable: plain bracket access traverses Object.prototype partial = options.partials[options.name]; ```</p> <p>`hasOwnProperty` is never checked, so if `Object.prototype` has been seeded with a key whose name matches a partial reference in the template (e.g. `widget`), the lookup succeeds and the polluted string is returned. The runtime emits a prototype-access warning, but the partial is still resolved and its content is inserted into the rendered output unescaped. This contradicts the documented security model and is distinct from CVE-2021-23369 and CVE-2021-23383, which addressed data property access rather than partial template resolution.</p> <p>**Prerequisites for exploitation:** 1. The target application must be vulnerable to prototype pollution (e.g. via `qs`, `minimist`, or any querystring/JSON merge sink). 2. The attacker must know or guess the name of a partial reference used in a template.</p> <p>## Proof of Concept</p> <p>```javascript…</p> <p><strong>Affected:</strong> npm: handlebars</p> <p>## Summary</p> <p>`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.</p> <p>## Description</p> <p>The root cause is in `lib/handlebars/runtime.js` inside `resolvePartial()` and `invokePartial()`:</p> <p>```javascript // Vulnerable: plain bracket access traverses Object.prototype partial = options.partials[options.name]; ```</p> <p>`hasOwnProperty` is never checked, so if `Object.prototype` has been seeded with a key whose name matches a partial reference in the template (e.g. `widget`), the lookup succeeds and the polluted string is returned. The runtime emits a prototype-access warning, but the partial is still resolved and its content is inserted into the rendered output unescaped. This contradicts the documented security model and is distinct from CVE-2021-23369 and CVE-2021-23383, which addressed data property access rather than partial template resolution.</p> <p>**Prerequisites for exploitation:** 1. The target application must be vulnerable to prototype pollution (e.g. via `qs`, `minimist`, or any querystring/JSON merge sink). 2. The attacker must know or guess the name of a partial reference used in a template.</p> <p>## Proof of Concept</p> <p>```javascript…</p> https://vulnerability.circl.lu/vuln/ghsa-2qvq-rjwj-gvw9