Slightly bloated LiPo; still save?
The common cause of bloating is either age, or abuse (or a combo of the two.) As the cells are used, the anode degrades, producing oxygen and leaving the Lithium and other element in a useless state. In addition the cathode slowly starts to produce metallic lithium. The oxygen produced by the anode bonds to the metallic lithium produced by the cathode, again limiting cell usability, and creating lithium "rust." However, the anode produces oxygen faster then the cathode produces metallic lithium for it to bond to. This means that the oxygen has nowhere to go, and pressurizes the cell, making it bloat out. This is also one of the reasons an overcharged cell will ignite under water without the presence of oxygen and air. Also due to lithium being HIGHLY reactive with water.

I've been working with LiPo batteries on one of my former jobs and we have had quite some 'issues' with  exploded or spontaneous ignition of LiPo batteries. Due to these experiences we replaced all bloated batteries directly and had fire and explosion proof containers for the batteries where we stored them in small amounts to prevent any issues or injuries.

I would recommend to stop using them as any current draw can increase the degradation and finally short the cells which is the main cause of the ignition or explosion of these batteries.