DOMPurify's ADD_TAGS function form bypasses FORBID_TAGS due to short-circuit evaluation
Summary
In src/purify.ts:1117-1123, ADD_TAGS as a function (via EXTRA_ELEMENT_HANDLING.tagCheck) bypasses FORBID_TAGS due to short-circuit evaluation.
The condition:
!(tagCheck(tagName)) && (!ALLOWED_TAGS[tagName] || FORBID_TAGS[tagName])When tagCheck(tagName) returns true, the entire condition is false and the element is kept — FORBID_TAGS[tagName] is never evaluated.
Inconsistency
This contradicts the attribute-side pattern at line 1214 where FORBID_ATTR explicitly wins first:
if (FORBID_ATTR[lcName]) { continue; }For tags, FORBID should also take precedence over ADD.
Impact
Applications using both ADD_TAGS as a function and FORBID_TAGS simultaneously get unexpected behavior — forbidden tags are allowed through. Config-dependent but a genuine logic inconsistency.
Suggested Fix
Check FORBID_TAGS before tagCheck:
if (FORBID_TAGS[tagName]) { /* remove */ }
else if (tagCheck(tagName) || ALLOWED_TAGS[tagName]) { /* keep */ }Affected Version
v3.3.3 (commit 883ac15)
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | dompurify | < 3.4.0 | 3.4.0 |
References
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N- Weakness (CWE)
CWE-783- Platform
- npm
- Package
dompurify- Disclosed
- 16.04.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-39q2-94rc-95cp - CC BY 4.0
Vulnerability history: dompurify
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 30
- First → latest
- 08.2020 10.2026
- Without a fix
- 1
- Exploited in attacks
- 0
Severity breakdown
- Critical 2
- High 3
- Medium 19
- Low 6
Disclosures per year
- 2020: 3
- 2021: 0
- 2022: 0
- 2023: 1
- 2024: 3
- 2025: 1
- 2026: 22
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DOMPurify's ADD_TAGS function form bypasses FORBID_TAGS due to short-circuit evaluation this entry
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