Those WhatsApp chats you thought you deleted may not be gone.
According to the iOS researcher Jonathan Zdziarski, WhatsApp retains and stores chat logs even after those chats have been deleted. According to a post first reported on by The Verge, Zdziarski examined disk images taken from the most recent version of the app, and found that the software retains and stores a forensic trace of the chat logs even after a user has deleted them. This supposedly creates an aggregation of information for anyone with physical access to the device. According to Zdziarski’s research, the same data can also be recovered through a remote backup system.
Despite the fact the data is marked as deleted by the app, it is not been overwritten and therefore is still recoverable through forensic tools, according to Zdziarski.
In April, WhatsApp switched to default end-to-end encryption through the Signal protocol. But that system only protects data in transit, preventing carriers and other intermediaries from spying on conversations as they travel across the network.
His most recent findings deal with what happens to that data after it reaches the phone, particularly when it’s stored on iCloud storage. WhatsApp messages are backed up by iCloud without hard encryption. Most notably, according to Zdziarski’s research, this means police could obtain clear records of conversations through a court order, even if the conversation had been deleted within the app.
“The core issue here is that ephemeral communication is not ephemeral on disk,” Zdziarski wrote in the post.
Fortune has reached out to WhatsApp and will update the story if it responds.