Google is fixing an issue with Android phones that could have exposed users' personal data.
It follows a warning from German security researchers that more than 99% of handsets were potentially leaking information.
The flaw meant hackers could have gained access to data within the phones' calendar and contacts applications.
Such issues are likely to become more frequent, warned security experts.
Google said in a statement: "We're starting to roll out a fix which addresses a potential security flaw that could, under certain circumstances, allow a third party access to data available in calendar and contacts.
"This fix requires no action from users and will roll out globally over the next few days."
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