Mozilla yesterday blocked a Skype add-on for Firefox, saying it caused more then 40,000 crashes of the browser last week and seriously slowed page loading.
One Mozilla manager called Skype a "repeat offender" when recommending that the company blacklist the add-on.
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Skype Toolbar, a Firefox extension bundled with the popular phone calling application, has been added to Mozilla's list of banned add-ons, said Mozilla in a blog post Thursday.
"The current shipping version of the Skype Toolbar is one of the top crashers of Mozilla Firefox 3.6.13, and was involved in almost 40,000 crashes of Firefox last week," said Mozilla. "Additionally, depending on the version of the Skype Toolbar you're using, the methods it uses to detect and re-render phone numbers can ... drastically affect the page rendering times of a large percentage of Web content."
Firefox users can still use the Skype Toolbar, as Mozilla has only "soft-blocked" it, meaning that although it has disabled the add-on, users can re-enable the extension after clicking through a warning message.
Mozilla, however, is considering "hard blocking" the add-on, according to a message on Bugzilla, the company's bug- and change-tracking database. That move would completely bar the Toolbar.
The Skype Toolbar detects phone numbers embedded in Web pages, then makes those numbers clickable so that users can more easily dial with the Skype desktop program. The Firefox add-on is installed by default when the desktop version of the VoIP software is installed or updated.
Mozilla said it had trouble reaching Skype's extension developers, one of the reasons it cited for blocking the add-on.
"Over the past two weeks we've doubled our efforts to contact the Skype extension team and several people at Skype have told us they pinged the extension team for us," said Justin Scott, Mozilla's add-ons product manager, in a comment on Bugzilla Wednesday. "We did not receive a response from them until this afternoon."
Skype declined to comment on the communications problem that Scott and others described on Bugzilla.
"Given the volume of crashes, the extent of the performance impact, the fact that users don't actually choose to install this add-on, and the extension team's lack of response during the weeks we were giving them to solve these issues, we should continue as planned to soft-block all versions of Skype in all versions of Firefox immediately," Scott said two days ago.
The Skype Toolbar has given Firefox users fits before. In 2008, a Bugzilla entry accused the add-on of causing the browser to hang, repeatedly reload pages and break links to PDF documents. After investigating, Mozilla added an older version of the extension to the Firefox blocklist.