No company likes situations like this. At the beginning of the year, we had a case that Sony Xperia T3 exploded. This time the problematic model is the last year flagship smartphone from Korean company, i.e. Samsung Galaxy S6 Edge+.
Safety of users is very important topic for all mobile manufactures. They check if the device is overheating. In most cases the root cause is wrong usage of the device, e.g. people hide a smartphone under the quilt then it is charging. They also buy cheap replacements of batteries or chargers.
Interestingly, this accident has happened when the smartphone had being charged by the original Samsung Galaxy S3 charger.
However, the repair centre claims that this is not the reason of this ignition. The faulty battery or damage of the smartphone is more probably. In my opinion, you should not afraid of old chargers. In this case, Samsung Galaxy S3 charger provides 1 A current at 5 V and Samsung Galaxy S6 Edge+ supports Quick Charge 2.0 solution, i.e. it can handle 2 A current at 9 V.