# CVE-2026-65904: cure53 DOMPurify XSS bypass in IN_PLACE mode via cross-realm nodes

Source: https://junglewise.ai/threats/cve-2026-65904-cure53-dompurify-xss-bypass-in-in-place-mode-via-cross-realm  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-23. Updated: 2026-07-23  
License: CC BY 4.0 with a link back

CVE-2026-65904 · Severity: medium · CVSS 4.7 · Published 2026-07-23

DOMPurify is a popular library used to clean HTML and prevent malicious scripts from running in web applications. A flaw in its 'IN_PLACE' optimization mode allows malicious code to bypass security checks if the content comes from a different window or iframe. If an application uses this specific setting to process content from other frames, an attacker could execute unauthorized scripts (Cross-Site Scripting), potentially leading to data theft or account takeover.

## Quick answers

**Is CVE-2026-65904 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-65904 being exploited in the wild.

**How severe is CVE-2026-65904?** Medium severity, with a CVSS score of 4.7, published 23 July 2026.

**Which products and versions are affected?** cure53 DOMPurify <= 3.3.3.

**Is there a fix for CVE-2026-65904?** A patch was published on 2026-07-23: Version 3.4.4 listed as unaffected/patched in VulnCheck data Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-65904 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-65904?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A vulnerability exists in DOMPurify's IN_PLACE sanitization mode due to an improper cross-realm check. The private _isNode() function utilizes an 'instanceof Node' check which fails when the provided element originates from a different window or realm (such as an iframe's contentDocument). When this check fails, DOMPurify incorrectly stringifies the element to '[object HTMLDivElement]', resets the IN_PLACE flag to false, and returns the original, unsanitized DOM node to the caller. An attacker can exploit this by providing a malicious element from a cross-window context, which will bypass all sanitization filters. While the vendor initially considered this an edge case, version 3.4.4 was later released to address the issue.

## Affected products

- cure53 DOMPurify <= 3.3.3

## Timeline

- 2026-04-01: advisory: GHSA-4w3q-35jp-p934 published
- 2026-07-23: disclosed: CVE-2026-65904 published
- 2026-07-23: patched: Version 3.4.4 listed as unaffected/patched in VulnCheck data

## References

- [https://github.com/cure53/DOMPurify/security/advisories/GHSA-4w3q-35jp-p934](https://github.com/cure53/DOMPurify/security/advisories/GHSA-4w3q-35jp-p934)
- [https://www.vulncheck.com/advisories/dompurify-before-cross-site-scripting-via-in-place-mode](https://www.vulncheck.com/advisories/dompurify-before-cross-site-scripting-via-in-place-mode)