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Moderate severityGHSA Advisory· Published Jun 15, 2026

DOMPurify IN_PLACE Sanitization Bypass via Attached Shadow Root Inside <template>.content

CVE-2026-49978

Description

If the HTML you give it contains a element, and inside that template there's an element with a shadow DOM attached to it, DOMPurify quietly skips over the shadow contents. Whatever the attacker put in there - an image with an onerror handler, a link with a javascript: URL, even a full script - survives untouched. The moment the application uses that template the way templates are meant to be used (cloning it and inserting the result into the page), the malicious payload comes along and runs as if it had never been sanitized. From there an attacker gets everything XSS normally gets them: session cookies, stored tokens, the ability to act as the user, and the ability to leave persistent payloads behind for the next person who visits.

advisory.pdf

poc.html

AI Insight

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Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
dompurifynpm
< 3.4.73.4.7

Affected products

31

Patches

Vulnerability mechanics

References

2

News mentions

0

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