Problem:

On rare occasions, one might find a random birthday cake, complete with still smouldering candles, sitting on a table within their home.

Nobody remembers putting it there, it's just there.

Solution:

You may dispose of the cake as you see fit. If you wish to consume it: only do so if it is an ice cream cake; but be advised that it is likely going to be surprisingly flavourless as it has likely spent most of its birthday magic. DO NOT attempt to re-light the candles and make a birthday wish, especially if it happens to be your birthday.

Cause:

If it is not an ice cream cake, then it is likely there because of a fail safe to prevent food poisoning. Wishing on a tainted cake will cause it to teleport somewhere away from the one who made the wish. Do not eat this cake, throw it away.

While most birthday cakes can grant small wishes, only an ice cream cake is powerful enough to alter the timeline and this is likely the case. The most likely scenario is that someone has been displaced within or removed from the timeline with a wish such as "I wish I was never born" or "I wish I got that job". Either way, your home belonged to someone else in the previous timeline and the ice cream cake is all that remains of that timeline. DO NOT ATTEMPT TO WISH ON THIS CAKE. While you may be tempted to re-light the candles and make a wish to undo the wish that altered the timeline. This will lock reality into a time loop of the wish being made and you undoing it and will eventually trigger a fail-safe coded into reality which will erase the cake and everyone and every thing that interacted with it from existence.