Say goodbye to your IP Camera's external plugin in Firefox, Chrome killed NPAPI Plugins a while ago and Firefox has been planning to follow since October 2015.
Mozilla to Drop Support for All NPAPI Plugins in Firefox 52, Except Flash
Starting with March 7, when Mozilla is scheduled to release Firefox 52, all plugins built on the old NPAPI technology will stop working in Firefox, except for Flash, which Mozilla plans to support for a few more versions.
NPAPI stands for Netscape Plugins API and is an ancient plugins infrastructure inherited from the old Netscape browser on which Mozilla built Firefox.
Mozilla to Drop Support for All NPAPI Plugins in Firefox 52, Except Flash