Created attachment 8834302 [details] Screenshot from Firefox User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:51.0) Gecko/20100101 Firefox/51.0 Build ID: 20170125094131 Steps to reproduce: When I open Indian Type Foundry website, I found Deccan Telugu font does not works as expected. Open https://www.indiantypefoundry.com/fonts/deccan-telugu to see it Actual results: న్ does not joining together with Deccan Telugu web font. Expected results: న్ should joining together as seen from Edge.
I see this in Firefox 51, but AFAICT it works as expected in Dev Edition (53) and Nightly (54); I'm guessing this has been fixed in a harfbuzz update. (You could bisect using mozregression --find-fix to confirm that.)
OK, thanks; so this is part of the HB 1.4.1 update -> resolving as a duplicate.