I don't know if it's exactly a bug, but probably from what I've read on DevForum it's an exploiter

[AyrezRBLX (Ayrez)]

I’m a developer of the game Race Clicker and I’ve seen this rather dubious Bug Report.
His Profile

notgood - Roblox

[bvetterdays (roman)]

This has already been reported in better detail, please add your info to the original report rather than creating a duplicate:

MarketplaceService:PromptProductPurchase throws error "do not run what you just ran (vulnerable function)" for some players

We have a bug in Sumo Simulator where some calls to MarketplaceService:PromptProductPurchase throws the error “do not run what you just ran (vulnerable function)”. We added debug logging to ensure that the player and the Developer Product ID to the call is correct, The products are not “third party products” and “third party sales” is enabled either way. The frequency of this happening in Sumo Simulator is about 2 times per minute and it is happening for multiple users. Purchases seems to wor…

And yes, it’s likely this error is emitted from exploit software being used by your players.

Also, in future, please title your bug reports clearly like the original one linked above, and add proper detail for engineers to be able to assist you