Severity
5.1
Medium severity
Details
- CVSS score
- 5.1
- CVSS vector
- CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- CWE ID
Overview
About vulnerability
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)