If it's sparking that means there's air between the two contacts. Personally I would replace the outlet and the cord, neither of which are hard. If it still sparks, it's electrician time.
Posted By: 61_Shasta
Date: Tuesday 11 June 2019, at 08:28 pm Recommended by
My completely amateur guess is that either the plug or the outlet started not making good contact which started some loose contact. Anytime a spark occurs across air it destroys either a small part of the plug or the cord or both. As it gets worse the gap grows to where there's active noticeable sparking.
I'll bet that if you replace both you'll be fine. However I note that you mentioned rental property. I'm guessing your insurance would love you to do an insured electrician rather than DIY.