According to Julian Evans, the option to send out these types of updates - whether the user has elected to tick the auto-update option or not - is written into the software's terms and conditions.
Evans says that he found out yesterday that Skype has apparently forced an update called the Skype Toolbar, an extension to Internet Explorer and Mozilla Firefox, even though, as a security researcher, he had not agreed to the feature.
"To be honest I would have liked to have had the choice as to whether I wanted it installed on my machine. Google Chrome works in the same way too. If you don't like this update policy you have a choice not to use the software", he says in his latest security blog.
"If you want to remove the Skype Toolbar then I suggest you follow the steps below:
Firefox: click on the orange Firefox button (or click on Tools if you have the Menu bar active) and choose Add-ons. You can then disable the offending add-on.
Internet Explorer: click on Tools > Manage add-ons > right click and choose Disable.
Note: You will need to disable the Browser Helper and Skype Plug-In add-ons
Update: This option in SKYPE > Tools > Options > advanced>(change) from automatic to notify me> save is no longer available from 5.3.0.111. This feature has been removed by Skype. The current version 5.3.0.116 also doesn't support this option and there are no plans to include this option in future versions."
According to Evans, the toolbar feature appears to be an update to get around the widely reported login in problems that many Skype users encountered at the end of May.
At the time, he notes, Skype advised users to run through a multi-step process which involved deleting a file called `shared.xml' which had become corrupted.
The Skype automatic update, he says, will fix this problem and users will not need to delete any file. Mac users will have also received this update.