For those of you looking for a workaround to make Viber coexist with other apps like Opera and Virtualbox depending on libcurl4 and uninstalling your Viber client, here's a workaround:
Visit Viber website, download the rpm version (Fedora) and convert the rpm package to deb using alien:
sudo apt-get install alien sudo alien --to-deb --scripts viber.rpm
Install the package:
sudo dpkg -i viber_126.96.36.1995-3_amd64.deb
I hope it helps.