Hi! I upgraded my Mac Pro 4,1 to Mavericks yesterday, and now there's a process called "Safari Web Content" for each tab in Safari, and each of them uses 100% of one CPU core. At first one of them even used 1000%, after I killed it it seems the free CPU cycles were divided between the remaining ones... Restarting or disabling extensions didn't help. Does anyone have any idea what might be causing this? Thanks in advance!