This is really a "WTF how could they ever think this is a good idea?" kind of vulnerability. Usually the kind of stuff you get from shady, incompetent startups, but this is Google...
https://trufflesecurity.com/blog/google-api-keys-werent-secrets-but-then-gemini-changed-the-rules
Google API Keys Weren't Secrets. But then Gemini Changed the Rules. ◆ Truffle Security Co.

Google spent over a decade telling developers that Google API keys (like those used in Maps, Firebase, etc.) are not secrets. But that's no longer true.

@hanno Google *is* a shady incompetent startup. It just has a lot of VC money.