Take out the cartridge and clean it with vacuum cleaner, as well as the printer. Then shake the cartridge above clean paper, check if there are some toner coming out. After this try to print again for at least 80pages of text print sample. Open the printer and check the cartridge if still leaking. Inspect the OPC, if there is any scrap clean it. Fiber of paper will accumulate inside printer. Printer need to be maintained regularly. If leaking persist replace the cartridge.