If you want to know if your Android smartphone is vulnerable to the current problem where USSD commands are sent to Android smartphones through websites using the TEL: URL type. You can check if your smartphone or tablet is potentially open to this security problem using:
If you open this URL in your smartphone or tablet browser and you get a window showing your IMEI, you can fix this vulnerability by installing the free App “NoTelURL” under:
https://play.google.com/store/apps/details?id=com.voss.notelurl
Now calls of the TEL: URL on websites are first catched by the app choice requester. So if this one pops up while browsing, you can redirect it to the NoTelURL app. Et voila.