Cart Rules Accidently Applied to Order

[jor]

On a shop (PS 1.6.1.7) of my customer we encounter a strange behaviour:

When an admin user creates a new cart rule and at about the same time a customer places an order, the cart rules gets applied to the order without any interaction.

We've seen this at least 2 times. The customers have never seen the cart rule code and didn't even do a thing about voucher codes. Still the cart rules were "magically" applied to their orders resulting in an invalid discount!

What can we do to fix this? I'm a developer myself, but we're struggling to reproduce this behaviour intentionally. Any help is appreciated.