This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Synology Photo Station. Although authentication is required to exploit this vulnerability, the existing authentication mechanism can be bypassed. The specific flaw exists within the SYNOPHOTO_Flickr_MultiUpload function. When parsing the prog_id parameter, the process does not properly validate a user-supplied string before using it to execute a call to file_put_contents. An attacker can leverage this vulnerability to execute code under the context of the PhotoStation user.