BlackBerry Ltd. said Monday that there is an “extremely small” risk to the security of BBM communications from the Heartbleed bug on devices powered by Apple Inc.’s iOS software or Google Inc.’s Android system. In an emailed statement, the company said it found that for an attacker to exploit the Heartbleed vulnerability on BBM for iOS and Android devices “an attacker would … have to execute a ‘man in the middle attack,’ which is extremely difficult to execute because of BlackBerry's secure technology infrastructure, making the risk...