The problem was first discovered a few days ago, showing that when you first log in and set-up your HTC Sense UI, you’re asked if HTC can collect data regarding your usage. The problem arises when the data is logged and collected by HTC, certain third-party apps can also access this data.
This whole process means that any personal data, to a certain degree, could be accessed by many people. So what kind of data is being collected? Well, it is collecting data that is specific to your phone, including your device ID and IMEI, your account names, your geo-location and phone numbers from your call-log.
HTC are fully aware on the problem, and although it is indeed a major flaw on HTC’s part, they will be pushing a patch through in the next couple of days.