I did research too but the only way I could find was to create a process and remove _apex_session before saving it to the database.
declare
l_apex_session varchar2(80);
begin
l_apex_session := '?_apex_session=' || :APP_ID || ',' || :APP_SESSION;
:P2_CONTENT := replace(:P2_CONTENT, l_apex_session, '');
end;