Sick Blur is a free Chrome add-on developed by fumycat. It falls under the category of Browsers and specifically the subcategory of Add-ons & Tools. This add-on is designed to blur out messages in VK, a popular social networking site, after switching tabs. To view the blurred messages, simply click on the extension button located to the right of the address bar.

With Sick Blur, users can maintain their privacy and prevent others from reading their VK messages when they are not actively using the tab. This add-on adds an extra layer of security and confidentiality to VK conversations.

Overall, Sick Blur is a handy tool for VK users who value their privacy and want to ensure that their messages remain hidden from prying eyes when they switch tabs on Chrome.