When you delete a chat in WhatsApp, you do so safe in the knowledge that any traces of the message has been wiped from your phone and the app's software. According to iOS researcher Jonathan Zdziarski that may not be the case. 

Zdziarski recently took to his blog to detail his findings and the implications, if true, could prove quite worrisome for WhatsApp users. The iOS researcher made the discovery while examining disk images taken from the most recent version of the app (2.16.7). There, he reportedly found evidence that the app's software retains and stores a forensic trace of deleted chats. 

What makes the discovery even more significant is that the information could be recovered from any remote backup system, says Zdziarski. He adds that the problem stems from an issue with SQLite library, which does not overwrite deleted data by default. As such, although a chat may look as if it has been deleted, the data has not been overwritten.

As The Verge points out, this issue is only exacerbated by WhatsApp's recent move to encrypt conversations in-app. Now, this discovery could give police a means of accessing data from the app that's backed up to the cloud, for example. It could also open up avenues for unauthorised access to WhatsApp conversations by anyone who has physical access to one's device.  

For now, WhatsApp has not released an official comment on Zdziarski's discovery, but this is certainly a developing story.