Bug 2547089 (CVE-2026-106444)

Summary: CVE-2026-106444 handlebars: Handlebars: Cross-Site Scripting via unescaped closing script tags in precompiled templates
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in Handlebars. This vulnerability allows a remote attacker to execute arbitrary script code through Cross-Site Scripting (XSS). When an application precompiles untrusted template text and embeds the generated output directly into an inline web script block, static content is not properly escaped for closing script tags. An attacker can craft a template that prematurely closes the script container, allowing injected malicious markup to run in the victim's browser session.
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Description OSIDB Bzimport 2026-10-06 19:45:29 UTC 
Handlebars provides the power necessary to let users build semantic templates. From 4.0.0 until 4.7.10, Handlebars.precompile() uses quotedString() in lib/handlebars/compiler/code-gen.js to emit static template text into generated JavaScript without escaping sequences that terminate an enclosing HTML script element. When an application precompiles attacker-controlled template text and embeds the generated source directly in an inline script element, a closing script delimiter can end the element and cause following attacker-controlled markup to be parsed and executed. Ordinary server-side rendering and precompiled templates served as external JavaScript files are not affected. This issue is fixed in version 4.7.10.