Front formatter can break markdown rendering

[Aveyron-RetD]

Describe the bug
A clear and concise description of what the bug is.

To Reproduce
Steps to reproduce the behavior:
Create a new file

Do a line with "***"

Insert three check box
[] one
[] two
[] three

Do another line with "***"

See this file

Expected behavior
File stays the same

Screenshots
After a while the file gets transformed into this and break all markdown

Reproduced in deck app nextcloud/deck#7882 (comment)
See nextcloud/deck#7882

Server details:

• Nextcloud version: 33.0.2
• PHP Version: [e.g. 8.2]
• Database: [e.g. MariaDB 10.6]

Client details:

• OS: [e.g. Windows/macOS/Ubuntu]
• Browser: [e.g. Firefox, Chrome]
• Browser version: [e.g. 22]
• Device: [e.g. iPhone6, desktop]

Logs

Nextcloud log (data/nextcloud.log)

Insert your Nextcloud log here

Browser log

Insert your browser log here, this could for example include:

a) The javascript console log
b) The network log
c) ...