According to Barra, these details are only collected to see the online status of participants and to route messages.
"No phonebook contact details or social graph information (i.e. the mapping between contacts) is stored on Cloud Messaging servers, and message content (in encrypted form) is not kept for longer than necessary to ensure immediate delivery to the receiver."
The update will also mean that for those that opt-in to the service, phone numbers sent to Xiaomi's cloud messaging servers will no longer be sent in clear text. In other words, if Xiaomi users opt-in to its service, the company will still be able view them, while making it difficult for others to do so.
Source: CSO Australia
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