Improper Encoding or Escaping of Output in handlebars.js - #VU153368
Published: October 6, 2026
Vulnerability identifier: #VU153368
CSH Severity: Medium
CVSS v4: 2.1 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-116
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to execute arbitrary JavaScript in a victim's browser.
The vulnerability exists due to improper encoding or escaping of output in quotedString() in lib/handlebars/compiler/code-gen.js when precompiling attacker-controlled templates for direct embedding in HTML script elements. A remote attacker can supply a crafted template containing a closing script tag followed by malicious markup to execute arbitrary JavaScript in a victim's browser.
A victim must view the resulting HTML document. Ordinary server-side rendering and precompiled templates delivered as external JavaScript files are not affected.
Affected software
handlebars.js
Remediation
Install security update from vendor's website.
handlebars.js - update to 4.7.10