Security of httpd (url string exploit?)

Hi. Logwatch on my CentOS VPS reported the following:

--------------------- httpd Begin ------------------------

A total of 1 sites probed the server 222.73.21.47

A total of 1 possible successful probes were detected (the following URLs contain strings that match one or more of a listing of strings that indicate a possible exploit):

/?-d%20allow_url_include%3DOn+-d%20auto_prepend_file%3D../../../../../../../../../../../../etc/passwd%00%20-n/?-d%20allow_url_include%3DOn+-d%20auto_prepend_file%3D../../../../../../../../../../../../etc/passwd%00%20-n HTTP Response 200

---------------------- httpd End -------------------------

--------------------- pam_unix Begin ------------------------

vsftpd: Unknown Entries: authentication failure; logname= uid=0 euid=0 tty=ftp ruser=Administrator rhost=92.86.139.111 : 105 Time(s) check pass; user unknown: 105 Time(s)

---------------------- pam_unix End -------------------------

Is this serious? What should I do next?

Thanks