One option is to install a second firefox on your HDD just for your cams:
(1) download latest firefox installer still working (afaik 54.0.1) from here:
Directory Listing: /pub/firefox/releases/54.0.1/win32/
(2) temporarily rename any firefox icon on your desktop, otherwise it might be overwritten.
(3) install it in a second folder, e.g. "C:\program files (x86)\Mozilla Firefox HIKVision"
(4) go to new install folder and execute "firefox.exe -p" in cmd (-p is for getting profiles selection menu)
(5) create new profile, name it e.g. HIKVision, exit Firefox when started.
(6) edit the new firefox icon on your desktop (or where it is), rename it to e.g. "Mozilla Firefox HIKVision", and add start options "-p HIKVision -no-remote", rename back your old icon from step (2).
(7) run "Mozilla Firefox HIKVision", disable automatic updates, do the necessary changes in about:config (see other postings here) for the npapi plugins to run again.
(8) run your default Firefox with option -p from cmd to select back default start profile.
That should be it.