Lock screen adware in the Play Store is nothing new. Last year, Google had a bit of an epidemic on its hands, when once beloved apps such as ES File Explorer starting showing unwarranted overlays while phones were charging. We saw a similar thing with the Peel Smart Remote app earlier this year, and the latest offender appears to be Hotspot Shield VPN.
This is a widely trusted app, with more than 50m downloads and a Play Store rating of 4.2 from almost 1m reviewers.
Hotspot Shield VPN developer in trouble over lockscreen ads and potential privacy concerns was written by the awesome team at Android Police.