This indicates a possible attempt to exploit a PHP remote File Inclusion vulnerability in TurnkeyWebTools PHP Simple Shop.
The vulnerability may allow remote attackers to spread malicious links or insert malicious links into web pages on legitimate websites. When victims visit these links, their web browsers are redirected to attacker controlled web pages.
TurnkeyWebTools PHP Simple Shop 2.0
System Compromise: Remote attackers can redirect victims to malicious websites and infect their computers.
Currently we are not aware of any vendor supplied patches for this issue