Mozilla has seen some shocking statistics regarding the ever-growing internet phone application, Skype. When Skype is installed, it also will include an extension for Firefox to help integrate some features into web pages. This is a good concept. However, multiple flaws exist in the extension that cause Firefox to crash or slow down.
Skype's toolbar extension detects phone numbers within web pages and transforms them into a clickable link which will then dial the number from the Skype desktop application. Since anyone who installs Skype also installs the extension by default, a large number of users have it and, according to Mozilla's list of top crashers for the latest stable version of Firefox, 3.6.13, Skype ranks up in second place, causing almost 40,000 crashes just last week.
Mozilla outlined the issues in a blog post, noting that in addition to crashes, the method that the Skype toolbar uses "to detect and re-render phone numbers can make DOM manipulation up to 300 times slower, which drastically affects the page rendering times of a large percentage of web content served today (plain English: to the user, it appears that Firefox is slow loading web pages). "
The browser giant's solution was to add all versions of the Skype Toolbar to the Mozilla Firefox Blocklist, which is a list of extensions that should not be used with Firefox. The entry made in the blocklist is a "soft block" where, simply speaking, the toolbar will be disabled automatically with a message displayed to the user alerting them of the block and its cause, but still giving them the option to re-enable it.
Mozilla wishes to note that only the toolbar within Firefox will be blocked, not the desktop application in any way. They have contacted the Skype Toolbar developers and will be working with them to correct the issues to allow the extension back into Firefox.