Well there is risk while charging any battery; low grade or mismatched cells without proper protection are of course more potentially dangerous in this regard than trusted brands with built-in overcharge/discharge circuitry, especially if the charger is not particularly up to snuff either. Think TrustFire was once a well respected original brand, but because it caught on so well others copied it with names like SingFire, LingsFire, LusteFire, TangsFire, FandyFire,WindFire, BurstintoFire, etc. From what I've read there are even fake TrustFires on the market now (impossible to verify.) Big part of the problem is that at present there is no commercially viable way to recycle lithium batteries, so the tons and tons of those headed to landfill are scooped up by the desperate and repackaged by the unscrupulous. Thus 50% or more of what seems a working battery pack might be dead weight, and the rest barely functional. Doesn't mean that every pack you buy for cheap will be complete garbage, just that there is little consistancy and what you get is pretty much the luck of the draw. Fairly decent cells are oft discarded alongside the duds, and manufacturers are still producing new cheap cells. Just have to be aware that the plant assembling your bicycle lamp generally has no relationship at all with that churning out the batteries, they are entirely different fields of endeavor. As mentioned TrustFire was at one time more reliable and perhaps they do actually produce both their own (mediocre) Li-ion cells as well as all those (fairly top-notch) LED lamps, they're a big company. But because of all the copycats, only sure way to guarantee you're getting genuine quality cells is to buy name brands from reputable vendors. Even the cheaper Chinese companies like MagicShine and I think also maybe NiteFighter and O-light include top of the line battery packs and fairly decent chargers along with their lamps. Yes you have to pay considerably more for them than for a Fire!Fire! but they're still a fraction of the price of a Lupine, and for those who intend to use their bicycle lights for any amount of time the cost is easily justifiable. OTOH if you're only going out on short jaunts and your lighting isn't all that critical, than sure, FlamingFire brand cells might be fine for your needs and you'll save like $40 to $60, nothing wrong with that. As long as you you've got good insurance on your house.

Hope I haven't scared you too much or discouraged you from enjoying your new light. Because even the lowest end LED/Li-ion setup nowadays will knock your socks off.

Enjoy the ride!