DOMPurify has a SAFE_FOR_TEMPLATES bypass in RETURN_DOM mode
Date: 2026-04
Affected: npm/dompurify
Attack vector: xss
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2026-41238
CVE-2026-41239
CWE: CWE-1289
CWE-1321
CWE-79
CVSS: 6.8 (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N)

## Summary | Field | Value | |:------|:------| | **Severity** | Medium | | **Affected** | DOMPurify `main` at [`883ac15`](https://github.com/cure53/DOMPurify/tree/883ac15d47f907cb1a3b5a152fe90c4d8c10f9e6), introduced in v1.0.10 ([`7fc196db`](https://github.com/cure53/DOMPurify/commit/7fc196db0b42a0c360262dba0cc39c9c91bfe1ec)) | `SAFE_FOR_TEMPLATES` strips `{{...}}` expressions from untrusted HTML. This works in string mode but not with `RETURN_DOM` or `RETURN_DOM_FRAGMENT`, allowing XSS via template-evaluating frameworks like Vue 2. ## Technical Details DOMPurify strips template expressions in two passes: 1. **Per-node** — each text node is checked during the tree walk ([`purify.ts:1179-1191`](https://github.com/cure53/DOMPurify/blob/883ac15d47f907cb1a3b5a152fe90c4d8c10f9e6/src/purify.ts#L1179-L1191)): ```js // pass #1: runs on every text node during tree walk if (SAFE_FOR_TEMPLATES && currentNode.nodeType === NODE_TYPE.text) { content = currentNode.textContent; content = content.replace(MUSTACHE_EXPR, ' '); // {{...}} -> ' ' content = content.replace(ERB_EXPR, ' '); // <%...%> -> ' ' content = content.replace(TMPLIT_EXPR, ' '); // ${... -> ' ' currentNode.textContent = content; } ``` 2. **Final string scrub** — after serialization, the full HTML string is scrubbed again ([`purify.ts:1679-1683`](https://github.com/cure53/DOMPurify/blob/883ac15d47f907cb1a3b5a152fe90c4d8c10f9e6/src/purify.ts#L1679-L1683)). This is the safety net that catches expre


Mitigations:

Architectural layers (MAESTRO):