This attack could pose a moderate security threat. It does not require immediate action.
This signature detects an attempt to execute arbitrary commands using Matt Wright's FormMail CGI program.
Matt Wright's FormMail is a web-based e-mail gateway.
In versions 1.9 and earlier, the "recipient" hidden field is not checked for the semi-colon(;), the shell command separation character, enabling an attacker to execute arbitrary command remotely.