I just checked the security logs of Zenphoto.
It is interesting to see the evolution of unsuccessful connect attemps from various IPs:
/zp-core/zp-extensions/uploader_jQuery/uploader.php (end of last year)
/zp-core/zp-extensions/zenpage/admin-pages.php (this month)
I assume there was a vulnerability in the uploader that has been fixed, and a new one in the Zenpage admin.