O2 accused of sharing customer phone numbers with websites

Customers of O2 have potentially had their mobile phone numbers sent to website they've visited.

A special webpage has been created that shows the information sent to a website when it is accessed from an O2 device. The developer of the website explains that the page uses a script that displays all the information received when a user visits it.

"If you're on O2's UK mobile network (not ADSL), you'll (probably) see a line beginning with x-up-calling-line-id - followed by your mobile phone number in plain text."

While some O2 customers have been seeing their phone number displayed, it isn't the case for everyone.

Disgruntled O2 customers have been complaining on Twitter, with the company responding by saying it was investigating the matter with its "internal teams" and that it hoped to share more information soon.

Users of Tesco mobile and Giffgaff will see similar results as they use O2's network. People on Vodafone, Orange, T-Mobile and other providers that use these networks have not been affected.

O2 customers can access the website on their mobile device by clicking here. The mobile number will only appear if it is being accessed over a mobile network.