The story
AdGuard was founded as a private company in Moscow, Russia in 2009, then later moved its headquarters to Cyprus.
During late 2014, the distribution of AdGuard's app for Android was removed from Google Play. It has since been made available for download from the developer's own website.
From the summer of 2018 to the summer of 2019, AdGuard for iOS received no updates due to Apple policies at the time against ad blocking via the iOS VPN APIs.
In September 2018, AdGuard was hit by credential stuffing attack. AdGuard claims that their servers were not compromised and instead attackers used credential pairs reused by victims on other sites and stolen from those other sites. According to company spokesperson, they "do not know what accounts exactly were accessed by the attackers," so the company had reset passwords for all accounts "as a precautionary measure". Also, AdGuard pledged to use "Have I Been Pwned?" API to check all new passwords for appearance in known public data leaks. Furthermore, they implemented more strict password security requirements.
In November 2020, Microsoft Edge Store and Chrome web store were infiltrated with fraudulent add-ons posing as various legitimate VPN browser add-ons, including NordVPN and AdGuard's VPN add-on. Subsequently, Microsoft and Google were alerted and actions were taken to remove the fake add-ons in the various browser stores.
From Wikipedia’s article on AdGuard, shared under CC BY-SA 4.0.4