an open invitation to somebody

Từ điển Oxford Advanced Learner 8th

an ˌopen inviˈtation (to sb) idiom
1. an invitation to sb to visit you at any time
2. if sth is an open invitation to criminals, etc, it encourages them to commit a crime by making it easier
•Leaving your camera on the seat in the car is an open invitation to thieves.
Main entry: ↑open_idiom