Security vendor FireEye says that it scanned Android apps for vulnerability to the Heartbleed flaw and found that apps which had been downloaded a total of 220 million times were vulnerable to the exploit. After the company contacted the developers about the problem, some of them applied patches, but as of April 17, 150 million downloads were still vulnerable.
"We haven't observed active exploits yet, but given the scale, it's important for Android users to be aware of the ongoing threat," said Hui Xue, a senior engineer at FireEye.
Heartbleed is a security vulnerability in OpenSSL, an open source encryption protocol used by many websites and technology companies. Some mobile development firms have also used it to encrypt data used by their Android apps.
FireEye also warns that many scanner products which claim to be able to check for the Heartbleed flaw aren't very accurate.