So RSS won't be supported anymore and other formats too.

Only the web HTML + CSS + JS will remain and Chrome is pushing implementations at a faster pace that the other browsers can not . There is effectively an attempt to capture the web by Google.

I remember the library for XLST used in browsers is not maintained by the big corporations. Ah it's LibXML.

The depreciation notice: https://groups.google.com/a/chromium.org/g/blink-dev/c/CxL4gYZeSJA/m/yNs4EsD5AQAJ

Ah yes, a maintainability thing "Chromium uses the libxslt library to process these transformations, and libxslt was unmaintained for ~6 months of 2025".

Usage of the JS XSLTProcessor API is fairly volatile, registering somewhere between 0.01% and 0.1% of page loads, averaging around 0.05% over time. These numbers are above the typical 0.001% deprecation threshold. Again, we feel that the increased potential for breakage is balanced by the reduced security risk to 100% of Chromium users.

It's for security reason? XSLT users hacked are 0. Where are the security vulnerability?