Whenever you see 0days reported by someone from Threat Analysis Group it means that Google (TAG is a team within google) used some advanced detection technique to discover someone, usually a nationstate, "in-the-wild" exploiting this.
Reading their blog gives insight on how they find these. For example, for CVE-2021-30869 they discovered on a "watering-hole" website (i.e. some group in china hacked a hong kong protesting website and hosted an 0day on it to exploit protestors' devices). I'm guessing Google has methods to scrape the entire web looking for these browser exploits
Reading their blog gives insight on how they find these. For example, for CVE-2021-30869 they discovered on a "watering-hole" website (i.e. some group in china hacked a hong kong protesting website and hosted an 0day on it to exploit protestors' devices). I'm guessing Google has methods to scrape the entire web looking for these browser exploits