> how does libxml2 know to decompress something? > > does it require you, as the caller, to explicitly tell it to?

In the entry point/function that we use, `xmlReadMemory` (https://gnome.pages.gitlab.gnome.org/libxml2/devhelp/libxml2...), it doesn't handle compressed XML at all.

But there are indeed others where it attempts to auto-detect compression, although as I understand it from the docs only ZLib compression is autodetected… though I suspect these may be out-of-date and it may autodetect any/all compiled -in compression algorithms.

Regardless, the fact that it links with liblzma is cause for concern, given the mechanism of operation of the liblzma/xz backdoor.