First time I have run across this- is spray foam an approved/acceptable method of covering a junction box (although I am not sure there is actually a junction box there)?
I stared at this for five minutes and still cannot figure out what it is.
attic mushroom…
Somewhere in there is a wire splice. The only thing I can think of is that a previous inspector wrote up an open splice or uncovered junction box in the attic space. Their remedy was to encase it in spray foam.
Pretty sure spray foam is not a UL listed enclosure/cover 
Not an acceptable JB cover. Should definitely make it onto your report. Could have been done by a " home energy efficiency" company filling every hole they can find with gunk.
Could also be an open raceway used to get cables up from below into the attic with no splice. The seal stops the chimney effect.