Millions of Android users could face charges of up to £150 on 'free' apps on the Google Play Store.
The apps will charge users after the 'free trial period' is over.
The apps take advantage of a loophole that sllows developers to charge over £150 when the free trial is up.
Researchers at Sophos have made the claims about the apps and what they refer to as "unscrupulous publishers".
They claim a loophole within the Google Play Market is being exploited.
This allows developers to charge after the free trial "if the user hasn’t both uninstalled the application and informed the developer."
Sophos states that the apps are not installing malware but are aking a lot of money for things as sumple as barcode reading or filtering photos.
Sophos says he app scam is "fleeceware" because it's a grey area in the Play Market model and not outright fraud.
It relies on users being complacence without the apps they're downloading and not checking what they're being charged.
Sophos said that 14 of the 15 apps that it reported to Google have now been removed.
However, it said "a subsequent search revealed another batch of apps" that were skirting the rules and charging a lot.
The researchers said that the 'scammer' developers “seem to be very good at staying under the radar.”
The apps involved appear innocent and include photo editors, GIF tools and calculators.
In most cases, the free trial period for the app was short.
Jagadeesh Chandraiah, a reporter for SophosLabs, wrote: "In the case of one QR code reader app, the developer charges users €104.99 after 72 hours, while the makers of Professional GIF Maker charge users €214.99.
"We haven’t seen apps sold at this price before."
