Assuming it’s not cached and sent next time it talks, of course.

Only their word until someone does it with a sniffer. E: I suppose, or looks the source but someone answered better now.

Note: Unlike other browsers that rely on cloud services, Firefox keeps your data safe on your device. There’s no privacy risk of sending text to third parties for analysis because translation happens on your device, not externally.

https://support.mozilla.org/en-US/kb/website-translation

Your ebike is also spying, probably.