These kinds of batteries are used in drill power packs, and other power tools etc.
They might even be used inside compact car jump starter packs (not the lead-acid battery ones).
There appears to be no information (- none that I could find so far) on the net about 18650 batteries self-igniting due to internal flaws or damage, or otherwise. So my assumption that it is relatively safe for the 'modern' (latest) kinds of car jump starters to be kept inside cars, or just left alone on a shelf inside the home?
So, as long as the item comes from a 'reputable' commercial store, then should the assumption be 'ok' to trust that it's not going to just ignite? So assume similar risk as tv, computer, video monitor, regular house-hold appliances?