Apple has said that it is preparing a software update to close a security hole pointed out by German authorities. The gap exists when users of the iPhone view PDF files, which leaves them exposed to forced installs of malicious software. Once infected by the software, ne'er-do-wells can access customer information such as emails, passwords, banking data, and calendars. "Apple takes security very seriously, we're aware of this reported issue and developing a fix that will be available to customers in an upcoming software update," said Apple in a statement. The company didn't say when the security update would become available.