GHSA-46fp-8f5p-pf2m Improper detection of disallowed URIs by Loofah `allowed_uri?`

• RubyGems loofah: >= 2.25.0, < 2.25.1 → fixed in 2.25.1

Summary `Loofah::HTML5::Scrub.allowed_uri?` does not correctly reject `javascript:` URIs when the scheme is split by HTML entity-encoded control characters such as `&#13;` (carriage return), `&#10;` (line feed), or `&#9;` (tab). Details The `allowed_uri?` method strips literal control characters before decoding HTML entities. Payloads like `java&#13;script:alert(1)` survive the control character strip, then `&#13;` is decoded to a carriage return, producing `java\rscript:alert(1)`. Note that the Loofah sanitizer's default `sanitize()` path is not affected because Nokogiri decodes HTML entities during parsing before Loofah evaluates the URI protocol. This issue only affects direct callers of the `allowed_uri?` string-level helper when passing HTML-encoded strings. Impact Applications that call `Loofah::HTML5::Scrub.allowed_uri?` to validate user-controlled URLs and then render approved URLs into `href` or other browser-interpreted URI attributes may be vulnerable to cross-site scripting (XSS). This only affects Loofah `2.25.0`. Mitigation Upgrade to Loofah >= `2.25.1`. Credit Responsibly reported by HackOne user `@smlee`.