CVE-2026-66010

Versions of handlebars prior to 3.0.8 or 4.5.3 are vulnerable to Arbitrary Code Execution. The package's lookup helper fails to properly validate templates, allowing attackers to submit templates that execute arbitrary JavaScript in the system. It is due to an incomplete fix for a previous issue. This vulnerability can be used to run arbitrary code in a server processing Handlebars templates or on a victim's browser (effectively serving as Cross-Site Scripting).

Recommendation

Upgrade to version 3.0.8, 4.5.3 or later.

DOMPurify before 3.4.12 fails to execute afterSanitizeElements hook for custom elements allowed via CUSTOM_ELEMENT_HANDLING.tagNameCheck, allowing attributes to bypass application security policies. Attackers can preserve sensitive attributes on custom elements that later re-inject them into innerHTML sinks, creating second-order XSS gadgets.

DOMPurify before 3.4.12 fails to execute afterSanitizeElements hook for custom elements allowed via CUSTOM_ELEMENT_HANDLING.tagNameCheck, allowing attributes to bypass application security policies. Attackers can preserve sensitive attributes on custom elements that later re-inject them into innerHTML sinks, creating second-order XSS gadgets.

DOMPurify before 3.4.12 fails to execute afterSanitizeElements hook for custom elements allowed via CUSTOM_ELEMENT_HANDLING.tagNameCheck, allowing attributes to bypass application security policies. Attackers can preserve sensitive attributes on custom elements that later re-inject them into innerHTML sinks, creating second-order XSS gadgets.

Versions of handlebars prior to 3.0.8 or 4.5.2 are vulnerable to Arbitrary Code Execution. The package's lookup helper fails to properly validate templates, allowing attackers to submit templates that execute arbitrary JavaScript in the system. It can be used to run arbitrary code in a server processing Handlebars templates or on a victim's browser (effectively serving as Cross-Site Scripting).

The following template can be used to demonstrate the vulnerability:

	{{#with split as |a|}}
		{{pop (push "alert('Vulnerable Handlebars JS');")}}
		{{#with (concat (lookup join (slice 0 1)))}}
			{{#each (slice 2 3)}}
				{{#with (apply 0 a)}}
					{{.}}
				{{/with}}
			{{/each}}
		{{/with}}
	{{/with}}
{{/with}}```


## Recommendation

Upgrade to version 3.0.8, 4.5.2 or later.

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-c2j3-45gr-mqc4. This link is maintained to preserve external references.

Original Description

DOMPurify before 3.4.12 fails to execute afterSanitizeElements hook for custom elements allowed via CUSTOM_ELEMENT_HANDLING.tagNameCheck, allowing attributes to bypass application security policies. Attackers can preserve sensitive attributes on custom elements that later re-inject them into innerHTML sinks, creating second-order XSS gadgets.

Versions of handlebars prior to 4.0.14 are vulnerable to Prototype Pollution. Templates may alter an Objects' prototype, thus allowing an attacker to execute arbitrary code on the server.

Recommendation

For handlebars 4.1.x upgrade to 4.1.2 or later. For handlebars 4.0.x upgrade to 4.0.14 or later.

DOMPurify before 3.4.12 fails to execute afterSanitizeElements hook for custom elements allowed via CUSTOM_ELEMENT_HANDLING.tagNameCheck, allowing attributes to bypass application security policies. Attackers can preserve sensitive attributes on custom elements that later re-inject them into innerHTML sinks, creating second-order XSS gadgets.

TuxCare rebuilt handlebars to address 1 CVE. Fixed in 1.3.0-tuxcare.1.

TuxCare rebuilt handlebars to address 3 CVEs. Fixed in 1.0.12-tuxcare.2.

TuxCare rebuilt dompurify to address 2 CVEs. Fixed in 2.5.9-tuxcare.5.

TuxCare rebuilt dompurify to address 3 CVEs. Fixed in 2.5.8-tuxcare.6.

TuxCare rebuilt dompurify to address 10 CVEs. Fixed in 2.3.0-tuxcare.1.

TuxCare rebuilt dompurify to address 16 CVEs. Fixed in 2.4.0-tuxcare.1.

TuxCare rebuilt dompurify to address 11 CVEs. Fixed in 2.4.3-tuxcare.1.

TuxCare rebuilt dompurify to address 14 CVEs. Fixed in 2.4.7-tuxcare.1.

TuxCare rebuilt dompurify to address 10 CVEs. Fixed in 3.2.3-tuxcare.3.

TuxCare rebuilt dompurify to address 34 CVEs. Fixed in 3.0.3-tuxcare.1.

TuxCare rebuilt dompurify to address 7 CVEs. Fixed in 3.1.6-tuxcare.7.

TuxCare rebuilt dompurify to address 11 CVEs. Fixed in 2.3.0-tuxcare.5.

TuxCare rebuilt dompurify to address 9 CVEs. Fixed in 2.4.0-tuxcare.5.

TuxCare rebuilt dompurify to address 12 CVEs. Fixed in 3.0.3-tuxcare.5.

TuxCare rebuilt dompurify to address 9 CVEs. Fixed in 2.4.7-tuxcare.5.

TuxCare rebuilt dompurify to address 12 CVEs. Fixed in 2.4.3-tuxcare.8.

TuxCare rebuilt dompurify to address 4 CVEs. Fixed in 3.2.7-tuxcare.3.

TuxCare rebuilt dompurify to address 2 CVEs. Fixed in 3.4.8-tuxcare.4.

TuxCare rebuilt dompurify to address 1 CVE. Fixed in 3.4.11-tuxcare.1.

TuxCare rebuilt dompurify to address 1 CVE. Fixed in 3.4.10-tuxcare.1.

TuxCare rebuilt dompurify to address 1 CVE. Fixed in 3.4.9-tuxcare.1.

TuxCare rebuilt dompurify to address 1 CVE. Fixed in 3.4.7-tuxcare.1.

TuxCare rebuilt dompurify to address 1 CVE. Fixed in 3.4.6-tuxcare.1.

TuxCare rebuilt dompurify to address 1 CVE. Fixed in 3.4.5-tuxcare.1.

TuxCare rebuilt dompurify to address 12 CVEs. Fixed in 3.1.3-tuxcare.2.

TuxCare rebuilt dompurify to address 9 CVEs. Fixed in 3.1.2-tuxcare.2.

TuxCare rebuilt dompurify to address 11 CVEs. Fixed in 3.1.4-tuxcare.2.

TuxCare rebuilt dompurify to address 9 CVEs. Fixed in 3.0.2-tuxcare.2.

TuxCare rebuilt dompurify to address 10 CVEs. Fixed in 3.0.9-tuxcare.2.

TuxCare rebuilt dompurify to address 11 CVEs. Fixed in 3.0.8-tuxcare.2.

TuxCare rebuilt dompurify to address 10 CVEs. Fixed in 3.0.1-tuxcare.2.

TuxCare rebuilt dompurify to address 13 CVEs. Fixed in 3.1.0-tuxcare.2.

TuxCare rebuilt dompurify to address 12 CVEs. Fixed in 3.0.11-tuxcare.2.

TuxCare rebuilt dompurify to address 8 CVEs. Fixed in 3.1.1-tuxcare.2.

TuxCare rebuilt dompurify to address 10 CVEs. Fixed in 3.2.6-tuxcare.2.

TuxCare rebuilt dompurify to address 1 CVE. Fixed in 3.0.6-tuxcare.2.

TuxCare rebuilt dompurify to address 9 CVEs. Fixed in 3.3.3-tuxcare.3.

TuxCare rebuilt dompurify to address 13 CVEs. Fixed in 2.3.10-tuxcare.3.

TuxCare rebuilt dompurify to address 5 CVEs. Fixed in 3.0.5-tuxcare.2.

TuxCare rebuilt dompurify to address 5 CVEs. Fixed in 3.0.4-tuxcare.2.

TuxCare rebuilt dompurify to address 12 CVEs. Fixed in 3.4.0-tuxcare.1.

Versions of handlebars prior to 3.0.8 or 4.5.3 are vulnerable to prototype pollution. It is possible to add or modify properties to the Object prototype through a malicious template. This may allow attackers to crash the application or execute Arbitrary Code in specific conditions.

Recommendation

Upgrade to version 3.0.8, 4.5.3 or later.

Versions of handlebars prior to 3.0.8 or 4.5.3 are vulnerable to Arbitrary Code Execution. The package's lookup helper fails to properly validate templates, allowing attackers to submit templates that execute arbitrary JavaScript in the system. It is due to an incomplete fix for a previous issue. This vulnerability can be used to run arbitrary code in a server processing Handlebars templates or on a victim's browser (effectively serving as Cross-Site Scripting).

Recommendation

Upgrade to version 3.0.8, 4.5.3 or later.

Root has patched GHSA-2cf5-4w76-r9qv in the handlebars package for Root:npm. Multiple fixed versions available.