I have followed the docs for confluence on enabling anonymous user access to spaces of which entailed setting the global permission and then setting the space permission. The space permission ONLY has View checked and all others unchecked however when browsing the page anonymously i have an edit option and it allows me to edit and save those changes.
It does note that any changes will be flagged as an anonymous user when editing the page but them being able to actually edit is not a good scenario.
This is the Space permissions themselves.

This is the Global permissions

These are the default space permissions found under global permissions in admin settings.