DIAGNOSIS A leak from the bottom usually points to an internal hose that's come loose, a cracked water reservoir, or a failed seal where the reservoir meets the base.
FIX Unplug it immediately and dry everything. The first thing to check is the water reservoir. Take it off and inspect the bottom for hairline cracks, especially around the silicone gasket. Next, check the small rubber seal on the machine where the reservoir sits. If it's misaligned or has coffee grounds on it, it won't seal. Clean it and reseat the reservoir firmly.
IF THAT DIDN'T WORK The leak is likely internal. There's a small silicone tube that connects the reservoir port to the pump. If this slips off or cracks, water will dump inside the case. Fixing this requires opening the base, which voids the warranty. If it's under warranty, contact Ninja.
HEADS UP Never pick up the brewer by the water reservoir when it's full. This can strain and crack the connection points. Always lift from the main body.