October 1, 2020
Portals are a new feature of the web which is similar to
iframes, but with more emphasis on speed and user experience. The
portal element is only available on Chromium-based browsers under a preference flag. The corresponding specification is still under active discussion.
Unfortunately, research of this new feature has discovered some critical issues, including new XS-Leaks 1.
ID Leaks #
Portals can be abused as an alternative to the ID Attribute XS-Leak. If a website sets framing protections, the same technique can be applied using the
portal element instead 2.