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Facebook plugs email address indexing bug

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Incident-prone social network monolith Facebook has plugged yet another security leak, this time involving the indexing by search engines of email addresses not listed on Facebook.

Thousands of email addresses submitted using Facebook's "Find a friend" feature that were not tied to a Facebook account wound up getting indexed by Google, according to Blogger Cory Watilo, who was among those affected. The "Find a Friend" feature allows friends to hunt for acquaintances on Facebook by email address, so those exposed have their so-called mates to thank for any exposure.

"One obvious problem is that spammers can easily scrape this data and add easily legitimate address to their lists, many of whom might not give their addresses to Facebook for a reason," Watilo writes.

The issue sparked a lively discussion thread on Hacker News.

Facebook changed its robot.txt file to prevent the search engine from indexing the relevant "opt out of emails from Facebook" page so that email address data can no longer be harvested by spammers or other miscreants.

However, it told the AllFacebook blog that that its actions were only a precaution and that the email address exposure resulted from users inadvisedly published their own addresses on mailing lists rather than a fault on its part.

We are investigating this situation but in cases we have identified, Facebook users have republished e-mails from Facebook elsewhere on the Internet, making public their own e-mail addresses. In some instances, these venues have been personal blogs or public mailing list archives such as Yahoo Groups. As a precaution, we have stopped indexing these pages in Google but cannot control users who choose to republish their e-mails in blogs or mailing list archives.

Security experts are unsure of the root cause of the problem in this case, but the snafu represents the latest in a long line of security snafus involving the site over recent weeks - a factor that means many are disinclined to give it the benefit of the doubt.

Over recent days many Facebook users have been hit by a run of clickjacking attacks, taking advantage of the social network's "Like" facility. The ruse results in users endorsing a page as something they like without necessarily realising they are recommending it to all of their Facebook friends and contacts.

A fortnight ago Facebook admitted that it mistakenly gave advertisers data that might be used to discover users' names and locations, contrary to its privacy policy. MySpace made much the same error which resulted from coding errors in failing to obscure the URL of the user's profile page before handing over reports to advertisers.

In the last month the social network has also grappled with a flaw that created a means for hackers to delete Facebook friends, and a bug that allowed users to eavesdrop on IM chats, forcing the social network to suspend the feature while it applied a fix.

That's just a sample of the security problems affecting Facebook since the start of May alone and ignores the privacy controversies brewing since the December privacy roll-back. These were made worse by more recent plans to share users' details with selected third-party sites that forced the site to simplify its privacy controls last week. ®

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