Open season. (n.d.). In YourDictionary. Retrieved from https://www.yourdictionary.com/open-season
(plural open seasons)
(hunting, sometimes followed by on or for to designate the kind of animal hunted) A period of time during the calendar year when authorities within a jurisdiction permit the unrestricted hunting of one or more kinds of animal wildlife.
(idiomatic, often followed by on or for) A situation in which someone is endangered, blamed, harassed, or opposed in a sustained manner by a number of others; a situation in which something is endangered or otherwise opposed.
(idiomatic, often followed by on or for) A situation in which or period of time during which some activity or circumstance routinely occurs.
English Wiktionary. Available under CC-BY-SA license.