Uncaught DOMException: CSSStyleSheet.cssRules getter: Not allowed to access cross-origin stylesheet

[eyaler]

Steps to Reproduce

1. go to https://web.archive.org/web/20240529185621/https://oulipoh.com/resen/
2. click one of the tags in the header
3. observe the exception in the console
4. remove the extension and observe there is no exception

Expected behavior:
extension should not break websites or require them to take special preventive measures. as a last resort extension should try to signal that it is the cause of the breakage

Actual behavior:
duckduckgo extension injects css as a data: string to the html head. this has several unexpected consequences:

1. pages relying on the last stylesheet in the head to be a something specific will retrieve an unexpected stylesheet
2. pages using CSSStyleSheet.cssRules will hit the exception:
   Uncaught DOMException: CSSStyleSheet.cssRules getter: Not allowed to access cross-origin stylesheet

Versions
Firefox 132 + duckduckgo 2024.10.16 on windows