Incorrect code block rendering on preview panel

[0xn3va]

Describe the bug
The data in the code block is interpreted as part of the markup in the preview panel.

To Reproduce
Steps to reproduce the behavior:

• Create or start edit any page
• Hide preview page
• Insert code block with xss payload, for example

• Show preview page and see many alerts

Same behaviour:

Expected behavior
The data in the code block is interpreted as text data in the preview panel.

Host Info (please complete the following information):

• OS: Ubuntu 16.04
• Wiki.js version: 2.0.12
• Database engine: postgres 9.5.19