This is an old enquiry, but had the exact same problem in Dec 2017, so posting this up for those who maybe looking for a different solution... I tried the java, caches and the cookies etc, but nothing worked - Here's how I stopped it:
In my case, the first problem was an overheating macbook pro, another poster said check CPU in Activity Monitor for usage and turn off anything over 75%.
On the activity monitor the Dashboard was showing up at 82%, but trying to close it was impossible, every time I clicked on the dashboard, in a flash, it redirected to www.facebook/tr/ - so I couldn't open, or close the Dashboard.
After clicking on it several times without luck, I noticed it was the Webclips widget, repeatedly loading gallery images from a travel website, but was somehow stuck in a loop and continuously loading. After trying to open Dashboard a dozen times I managed to drag the widget into the middle of the screen, then after more attempts, click on the ℹ icon on the widget, a split second before the redirect. This flipped the widget over to 'edit' mode and stopped it redirecting and closing the dashboard. Problem solved.
Dashboard opened normally, I closed the Websclips widget, the facebook redirect stopped, and my MacBook cooled off immediately and is now running at a normal temperature