Google APIキーは秘密ではなかったが、Geminiがルールを変えた

Google API Keys Weren't Secrets. But then Gemini Changed the Rules. Simon Willison’s Weblog

26th February 2026 - Link Blog

Google API Keys Weren't Secrets. But then Gemini Changed the Rules. (via) Yikes! It turns out Gemini and Google Maps (and other services) share the same API keys... but Google Maps API keys are designed to be public, since they are embedded directly in web pages. Gemini API keys can be used to access private files and make billable API requests, so they absolutely should not be shared.

If you don't understand this it's very easy to accidentally enable Gemini billing on a previously public API key that exists in the wild already.

What makes this a privilege escalation rather than a misconfiguration is the sequence of events.

A developer creates an API key and embeds it in a website for Maps. (At that point, the key is harmless.)

The Gemini API gets enabled on the same project. (Now that same key can access sensitive Gemini endpoints.)

The developer is never warned that the keys' privileges changed underneath it. (The key went from public identifier to secret credential).

Truffle Security found 2,863 API keys in the November 2025 Common Crawl that could access Gemini, verified by hitting the /models

Google are working to revoke affected keys but it's still a good idea to check that none of yours are affected by this.

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This is a link post by Simon Willison, posted on 26th February 2026.

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