I was thinking:
If the extension does not exist or if the extension is disabled,
It would send a 303 See Other to the index.php or other significant place.
Anyway, If we may get a problem like that, I think it's better if we create a page for the extensions. Some place (not the index.php... ext.php, as an example) to where all the requests to extension pages go. That pages makes sure that the extension is there and activated and then includes the extension information for execution.