In OJS 3.3 (and possibly in OJS 3.4 onwards) you can create your own pages via Website → Setup → Navigation → Add item → Custom page. It’s possible to enter any name in the field “Path” and accidentally overwrite existing system pages, because there’s not a specific subfolder for own pages, but something like “example.com/index.php/journal/%PATH%”). For example, you can create a page named “search” and overwrite the search page - or create a page “oai” and overwrite the access to the OAI interface. This should not be possible.
Here’s an example
The standard OAI interface for an OJS journal looks like this (my institution has set up a search engine, that indexes academic content world wide via OAI)
Create an own page named ‘oai’
The new ‘OAI’ interface page
To prevent this, a subfolder should always be created if you create an own page (like “example.com/index.php/journal/pages/%PATH%”)