An extension cord or power strip is convenient, but it should not replace a properly installed electrical circuit. Too many high-power appliances on one strip can overheat contacts and create a fire or short-circuit risk.
A warm plug, burning smell, crackling sound, darkened sockets, breaker trips or dimming lights indicate overload, weak contact or an undersized circuit.
Unplug the devices, stop using damaged cords and call an electrician. A professional can check the socket, wiring, breaker, grounding and install extra outlets where needed.