slippery slope

noun2

1. •
   (figurative) A chain of events that, once initiated, cannot be halted; especially one in which the final outcome is undesirable or precarious.

   • I think basing your actions off an assumption like that is a slippery slope that is going to get you in trouble.
   • She's gotten herself on a slippery slope to being dismissed.
2. •
   A logical fallacy in which a party asserts that a particular result will probably follow from a given decision or circumstance, without necessarily providing any rational argument for the likelihood of the assumed consequence.