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WhatsApp chats leave a record even after deletion, says security researcher

Conversations can reportedly be reconstructed from traces of trashed chats.

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Traces of deleted WhatsApp chats can linger on an iPhone, says security researcher Jonathan Zdziarski.

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If you're a WhatsApp user with an iPhone, your chats might not be as secure as you think.

Despite the popular messaging app's announcement earlier this year that it would encrypt all user data, a security researcher said Friday that the latest version of WhatsApp for Apple's iOS software for iPhones leaves some information vulnerable. The researcher, Jonathan Zdziarski, found traces of deleted chats, which can be pieced together into conversations, he said, and that's even if you've cleared or archived them.

Zdziarski wrote in a blog post that such traces can linger "for months." And he also said it looks like the only way to truly shred the chats is to delete WhatsApp from your phone. Zdziarski added that Apple's iMessage software also suffers from the problem, something he wrote about in March.

Neither Facebook-owned WhatsApp nor Apple immediately responded to a request for comment.

The issue of privacy and encryption -- coding messages so they can be read only by the intended recipient -- came to the fore in 2013 after Edward Snowden leaked secret documents about the US National Security Agency's appetite for gathering people's digital data.

It's since fueled spats between the tech industry and governments around the world. One in particular involved an FBI demand that Apple help hack into the iPhone of a terrorist. Another involved Brazilian law enforcement's desire to have access to WhatsApp users' chats.

Zdziarski said there's no need for WhatsApp users to panic about the deleted-chats issue but that they should be aware that law enforcement and others could potentially access supposedly trashed conversations. He also listed ways to mitigate the issue, here.

WhatsApp said in February that 1 billion people were using the app, on various devices.