I logged into to Magento's Admin panel to find it is broken. All the tabs & sub-tabs are appearing in distorted way. I'm attaching screenshot below. How this happened suddenly? Any idea?

[![enter image description here](https://i.stack.imgur.com/mPZ4Q.png)](https://i.stack.imgur.com/mPZ4Q.png)

[![enter image description here](https://i.stack.imgur.com/C423d.png)](https://i.stack.imgur.com/C423d.png)