I've been getting this popup every day for the past few days...
There is no application set to open the URL rstf3://
I cannot figure out what is generating it, nor what an rstf3 URL might even be.
Google came up blank, Console shows no reference to it at all; I had hoped it might at least give a clue as to what app was trying to request it.
iGetter is the only new app on here which could possibly fit the timeline; I'll try quitting it tonight & see if the message no longer appears, but I'd really like to know what it is & what app type might be used to handle it if it's a legit request.
Running OS X 10.11.5 on a Mac Pro 5,1 with both ethernet & Wifi connectivity, if relevant.