WhatsApp Glitch Allows Access to Previous Owner’s Messages After Phone Number Change

Abby Fuller, an Amazon employee, recently brought attention to an interesting flaw in the WhatsApp messenger. After installing WhatsApp on her new smartphone with a new phone number, she was surprised to find messages belonging to the previous owner of that number in the app. Fuller immediately questioned how this was possible and whether the new owner of her old number could also read her message history.

Fuller emphasized that both her smartphone and SIM card were brand new, not purchased secondhand, and WhatsApp had never been installed on the device before. The messages she discovered were not encrypted, but it was not a complete chat history—most likely, she found unread messages sent to the account after the number change, which had not reached the previous owner. WhatsApp is not supposed to store the full history of encrypted messages on its servers.

Soon after, other users commented on Fuller’s post, sharing similar experiences, indicating that this was not an isolated incident.

Why Does This Happen?

This issue is likely not a vulnerability in the traditional sense. WhatsApp does not receive notifications from mobile carriers and “doesn’t know” when a phone number is no longer in use or has changed owners. For this reason, WhatsApp developers recommend users delete old accounts and use the “Change number” feature in the app’s settings. According to official documentation, if a user ignores these recommendations, all unread messages are supposed to be permanently deleted after 45 days of account inactivity.

However, Fuller claims that in her case, much more than 45 days had passed. This suggests that the stated time frame may not be strictly enforced, or there may be a bug in the automatic message deletion mechanism, causing undelivered messages to be stored much longer than intended.

Security Concerns

Experts agree that the issue Fuller discovered is a serious security gap in WhatsApp. As a result, many users could unknowingly be at risk of data leaks if their old phone numbers are reassigned to new owners.