The Fallout 76 Reddit warns Fallout 76 players against playing on public servers until a fix comes to address a way hackers can steal inventory items (thanks DSOGaming). Here's the PSA:

As many of you might know, a recent hack has been developed for Fallout 76 on PC that gives hackers the ability to steal items out of your inventory. Your caps, scrip, access to various locations and stash box/scrap box items are safe. Your weapons and armor, and any other inventory items are not safe.

Edit to add: this is unrelated to person-to-person trading, which is safe. The stealing is done through a "remote" hack, which merely requires the hacker to be in your vicinity (within render distance).

Since there is no way of knowing what player is using the hack, the only way to avoid it, is to not play on a public server. If you or friends of yours have a Fallout 1st subscription, you might want to stick to playing on a private server for a while. If you do play on a public server, it might be beneficial to store your best weapons and armor. (Or maybe switch to that lower level character you've got lined up and don't really care about that much yet.)