Comment by zzo38computer
4 hours ago
XSLT seem like it could be something implemented with WebAssembly (and/or JavaScript), in an extension (if the extension mechanism is made suitable; I think some changes might be helpful to support this and other things), possibly one that is included by default (and can be overridden by the user, like any other extension should be); if it is implemented in that way then it might avoid some of the security issues. (PDF could also be implemented in a similar way.)
(There are also reasons why it might be useful to allow the user to manually install native code extensions, but native code seems to be not helpful for this use, so to improve security it should not be used for this and most other extensions.)
The lead dev driving the Chrome deprecation built a wasm polyfill https://github.com/mfreed7/xslt_polyfill. Multiple people proposed in the Github discussions leading up to this that Google simply make the polyfill ship with Chrome as an on-by-default extension that could be disabled in settings, but he wouldn't consider it.