## Summary Loofah's HTML5 sanitizer restricted only the `xlink:href` attribute on certain SVG elements to local, same-document references. Browsers also accept a plain `href` attribute as an alternative to the deprecated `xlink:href` per the SVG 2 spec, but Loofah did not apply the same restriction to it, allowing those elements to reference arbitrary external documents. ## Impact SVG `<use>` can load and render external SVG content by reference. If the referenced external SVG is same-origin