---
id: GHSA-8whx-365g-h9vv
title: >-
  Loofah `allowed_uri?` does not detect `javascript:` URIs split by named
  whitespace character references
summary: >-
  Loofah `allowed_uri?` does not detect `javascript:` URIs split by named
  whitespace character references
severity: low
cwe:
  - CWE-184
vendor: loofah
product: loofah
ecosystem: rubygems
affected:
  - 'loofah >= 2.25.0, < 2.25.2'
patched:
  - loofah 2.25.2
published: '2026-07-21'
updated: '2026-07-21'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-8whx-365g-h9vv'
references:
  - url: >-
      https://github.com/flavorjones/loofah/security/advisories/GHSA-8whx-365g-h9vv
  - url: >-
      https://github.com/flavorjones/loofah/commit/5e91af861e3cdab47b91dd0b81f3afdfd13a5e19
  - url: 'https://github.com/flavorjones/loofah/releases/tag/v2.25.2'
  - url: 'https://github.com/advisories/GHSA-8whx-365g-h9vv'
tags:
  - ghsa
  - rubygems
ingestedAt: '2026-07-21T15:51:23.763Z'
---

## Overview

## Summary

`Loofah::HTML5::Scrub.allowed_uri?` does not correctly reject `javascript:` URIs when the scheme is split or prefixed by the HTML5 named character references `&Tab;` (tab) or `&NewLine;` (line feed).

This is a bypass of the fix for [GHSA-46fp-8f5p-pf2m](https://github.com/flavorjones/loofah/security/advisories/GHSA-46fp-8f5p-pf2m), which handled the equivalent numeric character references (`&#9;`, `&#10;`, `&#13;`) but did not cover the named forms.

## Details

`allowed_uri?` decodes HTML entities with `CGI.unescapeHTML`, which handles numeric character references but not HTML5 named character references. Payloads like `java&Tab;script:alert(1)` are therefore left intact, so the method does not recognize the `javascript:` scheme and returns `true`. A browser, however, decodes `&Tab;` and `&NewLine;` to tab and line feed and strips them from the URL during parsing, producing `javascript:alert(1)`.

`&Tab;` and `&NewLine;` are the only relevant named character references: across the HTML5 named-character table, they are the only two that decode to characters the WHATWG URL parser strips from a URL (U+0009 and U+000A; there is no named reference for U+000D). `&nbsp;` / `&NonBreakingSpace;` decode to U+00A0, which browsers do not strip, so they aren't usable for this bypass.

Note that Loofah's default `sanitize()` path is **not** affected, because Nokogiri decodes or entity-escapes HTML entities during parsing before Loofah evaluates the URI protocol. This issue only affects callers of the public `allowed_uri?` string-level helper that pass it HTML-encoded strings.

## Impact

Callers that validate a user-controlled URL with `Loofah::HTML5::Scrub.allowed_uri?` and then render the approved value into an `href` or other browser-interpreted URI attribute may be vulnerable to cross-site scripting (XSS). This includes applications that call `allowed_uri?` directly, as well as higher-level features built on top of it, such as Action Text 8.2's markdown link validation.

## Mitigation

Upgrade to Loofah >= 2.25.2.

## Credit

Responsibly reported by GitHub user @connorshea.

## Affected packages

- `loofah >= 2.25.0, < 2.25.2`

## Remediation

Upgrade to a patched release:

- `loofah 2.25.2`