But hang on, hasn't this happened before?
Yes, FaceApp is back, two years after it first stormed the internet.
So why is it trending again? The app's resurgence may be partly to do with an unimaginatively named hashtag doing the rounds on social media.
What is the #AgeChallenge?
The #AgeChallenge "challenges" you to upload an image of yourself with the app's filter applied.
Various celebrities, such as Piers Morgan, have jumped on the bandwagon (something which didn't really happen when the app first came around), giving FaceApp much more exposure, and lending a few famous faces to its cause of viral dominance.
In the internet age, these things also come and go with calculated PR campaigns that pay influencers to promote apps and services, so it's quite possible something of the sort is going on here.
The options available this time around seem more in-depth too.
Not only can you make yourself age by a few decades, you can also smooth out any wrinkles to become reacquainted with the younger you. Or you can add a beard, make-up or change your hairstyle among other things.
Yes, the app's gender swapping feature is still in there - though it's slightly more buried now - but from what we could see, the app's option that controversially allowed you to change ethnicity has been removed.
Is it safe to use?
The app's first wave of popularity broke when security concerns were raised about FaceApp's access to your phone's photo library.
Earlier versions of the app were able to access your entire photo library, without users necessarily giving it permission to do so.
But it appears that while FaceApp's latest iteration doesn't have quite as much freedom to browse your images, there are still some worrying privacy issues at play.
Some users have reported that the app still has access to their photos, even though they have FaceApp's permissions set to 'never' on their phone.
While you may have restricted FaceApp's access to your photos, an Apple API introduced in iOS 11 allows you to pick one photo for the app to work its magic on.
In summary, FaceApp won't be able to access your entire camera roll, but it can still access the photos you say it can.
The app still uploads your images to the cloud to be processed, before downloading them back to your phone with the results.
The images are not altered 'on device', and FaceApp is allowed to use your name, username or any likeness provided in any media format it likes without you being paid for it, and you won't have any ability to have it deleted.
How does it work?
The app claims to use "advanced neural portrait editing technology" to "improve your selfie".
Put simply, an AI analyses your photo, and then applies filters to it in a way that best seems humanly plausible.
That's where fears that images may be being stored for further use come in - the AI presumably learns from its past mistakes, and relies on a database of face shapes and types to best compute its designs.
How can I use it?
If you're still intrigued and not put off by the prospect of your images potentially being used for nefarious means, the app is available to download for both Android and iOS devices.
Simply load up the app once it is installed, and follow the onscreen instructions.
You can either choose an existing photo from your library (the app even singles out selfies and photos containing faces to get you started), or take a brand new snap to mess around with.
Once you're happy (or unhappy) with your creation, you can download it to your phone, ready to upload it to the World Wide Web and partake in the #AgeChallenge.
A paid version of the app is also available, which offers users even more image altering features.