I am using Firefox ESR 52.3.0 (64-bit) on my imac 27" (2017) with macOS Sierra 10.12.6. When I using this Firefox surfing on Facebook, I input word in comment textbox and press enter to comment it, the text in the textbox do not be send, but add a line on it. When I press enter key many times, the textbox will gone. When I use messenger to chat on FB on Firefox also happend this problem, and the whole messenger box will gone. I want to refresh the FB page to let the messenger box back. I do not have this problem on Google Chrome. FB do not have any problem about use enter to send text on Google Chrome on this device.