Well, using "pkg info -r <package>" I've find out the plugin that is using libxslt is os-acme-client.
libxslt-1.1.43_1 -> py311-lxml5-5.4.0_2 -> py311-beautifulsoup-4.13.4_1 -> py311-dns-lexicon-3.21.1 -> os-acme-client-4.10
libxslt-1.1.43_1 -> py311-lxml5-5.4.0_2 -> py311-beautifulsoup-4.13.4_1 -> py311-dns-lexicon-3.21.1 -> os-acme-client-4.10