astro's client-side router has DOM Clobbering Gadget that leads to XSS

Vulnerability Description

The Astro web framework has a DOM Clobbering gadget in the client-side router starting in version 3.0.0 and prior to version 4.16.1. It can lead to cross-site scripting (XSS) in websites enables Astro's client-side routing and has *stored* attacker-controlled scriptless HTML elements (i.e., `iframe` tags with unsanitized `name` attributes) on the destination pages. This vulnerability can result in cross-site scripting (XSS) attacks on websites that built with Astro that enable the client-side routing with `ViewTransitions` and store the user-inserted scriptless HTML tags without properly sanitizing the `name` attributes on the page. Version 4.16.1 contains a patch for this issue.

References

• https://github.com/withastro/astro/security/advisories/GHSA-m85w-3h95-hcf9
• https://github.com/withastro/astro/commit/a4ffbfaa5cb460c12bd486fd75e36147f51d3e5e
• https://github.com/withastro/astro/blob/7814a6cad15f06931f963580176d9b38aa7819f2/packages/astro/src/transitions/router.ts#L135-L156