Over the past several years, “hidden sectors” have attracted a surge of interest in the particle physics community. I’ll summarize the underlying physics motivation and give an update on various search strategies. Most of the talk will focus on new bounds on dark sector models, emphasizing where Standard Model uncertainties still play a big part. In particular, we’ll examine bounds on "dark photons" from Supernova 1987A, where we have incorporated finite-temperature effects on the production and trapping for the first time, utilized a realistic model of the high-mixing parameter space, and shown the effect of systematic uncertainties from stellar progenitor models. Other hidden sector scenarios will be addressed as time permits.