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Firefox-maker Mozilla has acknowledged that user data from registered accounts of developers building add-ons for the popular Web browser was made available temporarily on the Internet.

A security researcher notified Mozilla Dec. 17 that a partial database containing the user accounts was left on a public server. The organization was later able to account for every download of the database, which indicated no serious risk to accountholders.

"This issue posed minimal risk to users, however, as a precaution, we felt we should disclose this issue to people affected and err on the side of disclosure," Chris Lyon, director of infrastructure security, said in a Mozilla blog Monday night.

The database included 44,000 inactive accounts using an older password technology. Mozilla erased the passwords, disabling the accounts. All current user accounts leverage a more sophisticated password technology that has been in use since April 9, 2009. Mozilla said the accounts of current add-on developers were not at risk in the snafu. Users of the older accounts have been notified of the security breach by email.

The ability to use add-on applications on Firefox is a key feature that greatly expands the browser's usefulness to many users. Such add-ons have had their own security problems. In July, Mozilla removed the "Sniffer" add-on that was intercepting login data and transmitting it to a third party Web site.

Five months earlier, two other add-ons also found to contain malware were removed from Mozilla's site, addons.mozilla.org. Both applications, the Sothink Web Video Downloader and the MasterFlier, installed Trojans on the user's computer. Once installed, the malware could only be removed using anti-virus software.

Mozilla has retooled its code-review policies to prevent malware-carrying add-ons. The organization now requires that all add-ons be subjected to a code review before they become publicly available on Mozilla's Web site.

SEE ALSO:

Mozilla Disables Firefox Add-On, Recommends Upgrade

Mozilla Removes Two Malicious Firefox Add-Ons

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