O2 Privacy Flaw Sends Users' Mobile Numbers to Visited Websites

o2 logoAs noted by think broadband, a privacy flaw in the way UK carrier O2 handles web traffic on mobile devices has resulted in users' mobile numbers being sent to any website visited from the device as part of the headers in the HTTP requests. While O2 is apparently still investigating the situation, it appears to have the potential for significant privacy-related issues.

If you're reading this news article using your O2 mobile phone, you'll be pleased to know that O2 have already sent us your mobile phone number within the HTTP headers which normally contain information about how content can be displayed on your device. These headers are not normally seen by users, and usually not logged by most websites, but the flaw allows malicious sites to get more personal information about you than you may be willing to share.

For example, if you open an e-mail which includes references to external images, the mere action of opening the e-mail would divulge your phone number. This could be used by anyone undertaking a phishing attack or other scam to get more information from you. The opportunity to abuse this is potentially endless.

The issue was discovered by Twitter user @lewispeckover, who then set up a website to allow users to see what headers are being sent as part of their HTTP requests to websites.

He now notes that the headers coming from his device appear to have stopped showing his mobile phone number, although O2 has yet to issue an official statement on the matter. The company's Twitter account is continuing to blast out responses to concerned users, noting only that the company is looking into the situation and will issue an update when it knows more.

The issue is not exclusive to the iPhone and has the potential to affect all mobile data on the second-largest carrier in the UK, although some users have reported that they are not seeing their mobile numbers appearing in their HTTP request headers. The issue has the potential to for a significant impact on UK iPhone users, as O2 has proven to be a popular choice for iPhone users dating back to its status as the exclusive iPhone carrier in the UK when the device originally launched back in 2007.

Those familiar with the UK's privacy laws have indicated that mobile phone numbers are not considered protected information, but the disclosure of such numbers as part of standard HTTP requests does have the potential to carry implications for users.

Popular Stories

iOS 26

15 New Things Your iPhone Can Do in iOS 26.2

Friday December 5, 2025 9:40 am PST by
Apple is about to release iOS 26.2, the second major point update for iPhones since iOS 26 was rolled out in September, and there are at least 15 notable changes and improvements worth checking out. We've rounded them up below. Apple is expected to roll out iOS 26.2 to compatible devices sometime between December 8 and December 16. When the update drops, you can check Apple's servers for the ...
ios 18 to ios 26 upgrade

Apple Pushes iPhone Users Still on iOS 18 to Upgrade to iOS 26

Tuesday December 2, 2025 11:09 am PST by
Apple is encouraging iPhone users who are still running iOS 18 to upgrade to iOS 26 by making the iOS 26 software upgrade option more prominent. Since iOS 26 launched in September, it has been displayed as an optional upgrade at the bottom of the Software Update interface in the Settings app. iOS 18 has been the default operating system option, and users running iOS 18 have seen iOS 18...
iOS 26

Apple Seeds iOS 26.2 and iPadOS 26.2 Release Candidates to Developers and Public Beta Testers

Wednesday December 3, 2025 10:33 am PST by
Apple today seeded the release candidate versions of upcoming iOS 26.2 and iPadOS 26.2 updates to developers and public beta testers, with the software coming two weeks after Apple seeded the third betas. The release candidates represent the final versions of iOS 26.2 and iPadOS 26.2 that will be provided to the public if no further bugs are found during this final week of testing....
Photos App Icon Liquid Glass

John Gruber Shares Scathing Commentary About Apple's Departing Software Design Chief

Thursday December 4, 2025 9:30 am PST by
In a statement shared with Bloomberg on Wednesday, Apple confirmed that its software design chief Alan Dye will be leaving. Apple said Dye will be succeeded by Stephen Lemay, who has been a software designer at the company since 1999. Meta CEO Mark Zuckerberg announced that Dye will lead a new creative studio within the company's AR/VR division Reality Labs. On his blog Daring Fireball,...
iOS 26

When Will Apple Release iOS 26.2?

Monday December 1, 2025 4:37 pm PST by
We're getting closer to the launch of the final major iOS update of the year, with Apple set to release iOS 26.2 in December. We've had three betas so far and are expecting a fourth beta or a release candidate this week, so a launch could follow as soon as next week. Past Launch Dates Apple's past iOS x.2 updates from the last few years have all happened right around the middle of the...
maxresdefault

iPhone Fold: Launch, Pricing, and What to Expect From Apple's Foldable

Monday December 1, 2025 3:00 am PST by
Apple is expected to launch a new foldable iPhone next year, based on multiple rumors and credible sources. The long-awaited device has been rumored for years now, but signs increasingly suggest that 2026 could indeed be the year that Apple releases its first foldable device. Subscribe to the MacRumors YouTube channel for more videos. Below, we've collated an updated set of key details that ...
Intel Inside iPhone Feature

Apple's Return to Intel Rumored to Extend to iPhone

Friday December 5, 2025 10:08 am PST by
Intel is expected to begin supplying some Mac and iPad chips in a few years, and the latest rumor claims the partnership might extend to the iPhone. In a research note with investment firm GF Securities this week, obtained by MacRumors, analyst Jeff Pu said he and his colleagues "now expect" Intel to reach a supply deal with Apple for at least some non-pro iPhone chips starting in 2028....
ive and altman

Jony Ive's OpenAI Device Barred From Using 'io' Name

Friday December 5, 2025 6:22 am PST by
A U.S. appeals court has upheld a temporary restraining order that prevents OpenAI and Jony Ive's new hardware venture from using the name "io" for products similar to those planned by AI audio startup iyO, Bloomberg Law reports. iyO sued OpenAI earlier this year after the latter announced its partnership with Ive's new firm, arguing that OpenAI's planned "io" branding was too close to its...
iphone air camera

iPhone Air's Resale Value Has Dropped Dramatically, Data Shows

Thursday December 4, 2025 5:27 am PST by
The iPhone Air has recorded the steepest early resale value drop of any iPhone model in years, with new data showing that several configurations have lost almost 50% of their value within ten weeks of launch. According to a ten-week analysis published by SellCell, Apple's latest lineup is showing a pronounced split in resale performance between the iPhone 17 models and the iPhone Air....
iPhone 17 Pro Cosmic Orange

iPhone 17 Pro Lost a Camera Feature Pro Models Have Had Since 2020

Thursday December 4, 2025 5:18 am PST by
iPhone 17 Pro models, it turns out, can't take photos in Night mode when Portrait mode is selected in the Camera app – a capability that's been available on Apple's Pro devices since the iPhone 12 Pro in 2020. If you're an iPhone 17 Pro or iPhone 17 Pro Max owner, try it for yourself: Open the Camera app with Photo selected in the carousel, then cover the rear lenses with your hand to...

Top Rated Comments

Elijahg Avatar
181 months ago
I've really not been impressed by O2 in recent years. I first joined them in 2006, but ever since then, their network coverage in the 20 mile radius of here (near Bath) hasn't improved one bit. The 3G coverage is absolutely awful. If you aren't in a major town or a city, you have no chance of 3G with O2, only dial-up speed GPRS. Not even EDGE in most cases.

Everything Everywhere are very good, but Three (in the south of England at least) are best by far for 3G coverage.

Perhaps if O2 spent more money on, well, being a service provider and improving their network, rather than all that "priority moments" crap, they might increase their 3G coverage.
Score: 6 Votes (Like | Disagree)
Elijahg Avatar
181 months ago
Not so in my o2 account with an iPhone using iOS 5.0.1 via Safari.

It wasn't inserted into the user agent, it was a separate header: "x-up-calling-line-id".
Score: 4 Votes (Like | Disagree)
japanime Avatar
181 months ago
The "O" is for "Oops!"
Score: 4 Votes (Like | Disagree)
0098386 Avatar
181 months ago
I'm appalled they let this in.

I'm thrilled they fixed it so quickly.

I'm going to treat o2 with a bit more suspicion from here on out.
Score: 2 Votes (Like | Disagree)
The Phazer Avatar
181 months ago
I am now intrigued though as to who the "trusted partners" are. O2 themselves and BT Openzone are the only ones I can think of.

One is Bango, the company that runs O2's adult verification software and thought sending credit card numbers in plaintext over http was a good idea.

O2 might "trust" them. I don't.

Phazer
Score: 2 Votes (Like | Disagree)
4D4M Avatar
181 months ago
I'm perfectly happy with O2, I've found the coverage decent and I don't get loads of junk text messages from them like I did from Vodafone*. This latest gaffe is a bit annoying, but whatever, as a business owner my details are well and truly 'out there' for all the lowlife to exploit anyway. Bring it on scumbags.

*The junk texts don't stop when you leave Vodafone. The other day I received a text that said "Come back to Vodafone and we'll give you a free Windows 7 laptop". If there's one thing that would be guaranteed to STOP me going back to them, it's the threat of a crappy low end piece of junk with a crappy low end OS turning up at my house.
Score: 2 Votes (Like | Disagree)