Google is quietly tying one phone number to every account signed in on your Android phone.
According to a report, the behavior surfaces when a user has multiple Google accounts active on the same device: verifying a phone number for one account appears to extend that same number to the others, without a separate opt-in for each account. The linkage isn't surfaced anywhere obvious in account settings, and it's unclear whether this is a deliberate anti-abuse measure or a side effect of how Android handles multi-account sign-in. Google hasn't publicly detailed the mechanism, and the report treats it as a discovered behavior rather than an announced feature.
That matters because a phone number is one of the strongest identifiers Google has for tying together identities that users deliberately kept separate, whether for work, personal use, or privacy. If one number quietly threads multiple accounts together, the wall between them gets thinner, whether or not any actual data crosses over.
Google has spent a decade training users to hand over a phone number as a security backstop. Quietly using that same number to connect accounts is a good way to make people regret it.