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We've all suspected - and known - for ages that our mobile devices are checking up on what we do.
However, WhatsApp has made a point of stating over the years that they are the most secure messaging app going.
It is definitely the least invasive of all the services owned by Facebook, but that isn't going massively far, when you think about it.
Also, it's worth assuming that all apps are mining your personal data in some shape or form.
WhatsApp tells you about what personal data they keep on you in the terms and conditions that you were supposed to read when you signed up, but who has the time to do that, right?
Now, the folks behind the iPhone - and crucially iMessage - have shined a light on the information apps are actually grabbing from you.
On 14 December last year, Apple introduced new privacy labels that explain what data every app in the App Store is harvesting from you.
When you look up an app, a label is shown that tells you exactly what data it will be collect. This includes Apple's own products.
According to that, WhatsApp takes info such as contacts and location from you.
It could also get hold of your email address, financial information, phone number, and user content. That could all be linked to your identity.
Before Apple's scheme was rolled out, WhatsApp criticised it for being too vague.
The company said it doesn't tell the full story and isn't representative of how far the developers have gone to ensure that personal information is protected.
It said: "While providing people with easy to read information is a good start we believe it's important people can compare these privacy nutrition labels from apps they download with apps that come pre-installed, like iMessage.
"Our teams have submitted our privacy labels to Apple but Apple's template does not shed light on the lengths apps may go to protect sensitive information.
"While WhatsApp cannot see people's messages or precise location, we're stuck using the same broad labels with apps that do.
"We think labels should be consistent across first and thirty party apps as well as reflect the strong measures apps may take to protect people's private information."
For instance, the location that WhatsApp tracks is pretty broad, and links only to the IP address and country code that you have on your phone number.
They also only collect financial information if you're using Facebook Shops, which isn't even available in the UK or the USA.
However, it's not completely blameless. Some of the tags are deserved.
Data on purchases is later shared with Facebook to influence the things that will be targeted at you as advertising.
"Facebook will not use your WhatsApp messages for any purpose other than to assist us in operating and providing our Services."
Speaking about their rollout of privacy labels, Apple has said: "Every one of the more than 1.8 million apps on the App Store is required to follow strict privacy guidelines and report how it uses your data.
"And every app is rigorously reviewed by a team of experts at Apple.
"When you're checking out an app, you'll get a summary of privacy practices to help decide if it works for you. Apps you choose to download need your permission to access information like photos or location - and you can always change your mind about what you share."
The CMA - the UK's Competition and Markets Authority - has hailed Apple's decision as a victory for the consumer, as well as a step forward for data privacy.
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