When I bought my house I bought a $200 FLIR Camera that attaches to your phone, the FLIR One. I bought it to check windows and a doors for air leaks, and to check where I needed more insulation

Above my bathroom there was a lot of insulation, but there was a weird hot spot near a light. Why?

I went up into the attic and dug through the insulation, and I found this

Its a very, very, very badly done splice from a 12/2 feed of Aluminum romex to 14/2 Copper romex which was extremely hot to the touch

Not only that, but it was on a 20a non-AFCI breaker. both 12/2 Alu and 14/2 CU is only allowed on a 15a breaker

Not only is this not even in a junction box, but you can't just use regular wire nuts to join CU to Alu. You must used approved methods

I thew in a junction box and used some Alumiconn connectors to properly join the wires

This alone paid me the $200 back for the camera, this causing a house fire would cost well over $200