Hi, all. Hopefully I'm asking this in the right place. It's 2am and I am desperate for answers.
Tl;dr: Am I correct in assuming that whoever flashed openwrt to my router might have also added something else that might hang on through several resets and a re-flash to stock firmware? Context is below.
So... I had a small internet outage a few hours ago and thought nothing of it. Went to get on my tablet and noticed my wifi was down despite having internet connectivity via wire on my desktop. Did some sleuthing, discovered that I couldn't log in to my router's management gui... Reset it a few times, same thing. Checked for wifi and found a new said called "openwrt"
Lo and behold, it would seem that someone who is not me installed openwrt on my router and attempted to hide it. This was confirmed by using putty to ssh into "email@example.com" and seeing the big banner for Openwrt.
I figured out how to re-flash my router's original firmware, and am seemingly back in full control, but I'm not familiar with openwrt. I don't know but what openwrt made it possible for there to be software running on my router that might still be there even after I flashed the stock firmware back.