Package: firefox-esr Followup-For: Bug #861304 Hi Vincas,
I experienced a similar issue with my firefox after upgrade 45.9 to 52.2. Some fonts, namely Helvetica, looked weird and clearly lacked support of Czech language. I've traced to problem back to fontconfig. I resolved the issue by upgrading the fontconfig packages to stable version and running dpkg-reconfigure fontconfig-config as recommended by https://wiki.debian.org/Fonts. Restart of firefox, or other affected program, is required. Also the broken link in /etc/fonts/conf.d was fixed. The change of fonts can be observed using fc-match. Before the fix it returned $ fc-match Helvetica helvR12-ISO8859-1.pcf.gz: "Helvetica" "Regular" Note especially the ISO8859-1 encoding. After the reconfigure $ fc-match Helvetica texgyreheros-regular.otf: "TeX Gyre Heros" "Regular" Not it looks fine. Hope this helps. Vlastik
