Possible XSS bug #1531

Describe the bug
Create or edit a page
Steps To Reproduce
Steps to reproduce the behavior:

1. create or edit a page
2. add some text hit enter
3. add malicious or even innocuous javascript
4. you get the pop up on save or any refresh.

Expected behavior
This should be filtered and sanitized so it doesn't actually execute.

Screenshots
Attached

Your Configuration (please complete the following information):

• Exact BookStack Version (Found in settings): BookStack v0.26.2

• PHP Version: 7.2.19

• Hosting Method (Nginx/Apache/Docker): Apache

Additional context
I have none.