Is it permissible to use cosmetics purchased from someone at a very low price, with the suspicion that they might be stolen?

Mere doubt that the seller is an aggressor does not affect [the ruling], nor does the presumption of his selling cosmetics for less than their value, because they are susceptible to damage. Therefore, there is no harm in benefiting from these things, for the unknown is like the non-existent, and the default assumption regarding what is in the possession of a Muslim is that it is his property if he claims so.