O2 has fixed the issue that causes customers' mobile numbers to be shared with websites they visit from their phones.
In a post on its own site, the network admitted that between 10 January and 2pm today, customers' phone numbers could have been accessed by sites that don't belong to the network's roster of 'trusted partners'.
The problem was sparked by technical changes during routine maintenance that "had the unintended effect" of letting website owners see the digits of people accessing their site.
You will only have been affected if you were browsing over 3G or WAP services -- if you were connected over Wi-Fi then your number won't have been shared.
O2 says it shares your mobile number with its partners in order to do things like manage age verification and let third-party sites bill you for things like ringtones or downloads. The breakdown meant sites outside those trusted partners could see your phone number.
Many customers may find the fact that O2 shares your digits with any third parties at all rather rum news, but the thought that for a period of two weeks loads more sites could have been peeking at your number is somewhat disconcerting.
O2 deserves credit for fixing this problem quickly, but the question now is what happens next. The BBC reports that the government's Information Commissioner is investigating the security breach, something with which O2 has said it will be "co-operating fully". The network also says it has contacted broadcasting watchdog Ofcom.
We suspect O2 customers will want to know if they can expect anything in terms of compensation, or if there's any way to find out which websites may have accessed their mobile number. We've asked O2 about this, and we'll let you know if we hear anything.
Are you an O2 customer? Has this breach caused you to lose faith in the network? Tell us in the comments, or on our Facebook wall.