The file is
install.rdf
, and it's located at ~/Library/Application Support/Firefox/Profiles/.default/extensions/iViewFox@forboden.com/install.rdf
. It's an XML file that can be edited in your favourite text editor. In the file there's a line that says:
<em:maxVersion>4.0.*</em:maxVersion>
which I changed to:
<em:maxVersion>7.0.*</em:maxVersion>
Restarted FireFox, and the Add On seems to be functioning correctly.