Hi Giampaolo,
I know next to nothing about modsecurity I'm afraid.
I looked at the file and I can tell you that the first part is a url_encoded string that is the form data that ChronoForms creates and saves from the Wizard.
The next past appears to the the main error message:
--14dfb831-H--
Message: Access denied with code 403 (phase 2). Match of "rx (/\\?q=node/[0-9]+/edit$)" against "REQUEST_URI" required. [file "/etc/modsecurity2/asl/10_asl_rules.conf"] [line "781"] [id "380018"] [rev "6"] [msg "Atomicorp.com WAF Rules: Potentially malicious PHP code injection attempt"] [data "set\x22"] [severity "CRITICAL"]
Apache-Error: [file "core.c"] [line 3650] [level 3] File does not exist: /home/alfierii/domains/example.it/public_html/403.shtml, referer: http://www.example.it/administrator/index2.php?option=com_chronocontact
Action: Intercepted (phase 2)
Apache-Handler: x-httpd-php5
Stopwatch: 1294328428955060 464585 (430720* 463830 -)
Producer: ModSecurity for Apache/2.5.12 (http://www.modsecurity.org/); core ruleset/1.6.0.
Server: Apache/2
I Googled around a bit and the line 781 reference seems to come from this part of the rule set
#code injection attempt
SecRule REQUEST_BODY|REQUEST_URI_RAW|XML:/* "< ?[?%] ?php" \
"phase:2,t:none,t:urlDecodeUni,t:htmlEntityDecode,t:replaceNulls,t:compressWhiteSpace,t:lowercase,pass,nolog,skip:1"
SecAction phase:2,pass,nolog,skipAfter:END_PHP_CODE_INJECTION_ATTACKS_2
SecRule REQUEST_BODY|REQUEST_URI_RAW|XML:/*|!ARGS:filecontent "(?:define|fgets|move_uploaded_file|readfile|ftp_put|ftp_fget|gzencode|ftp_nb_put|bzopen|readdir|gzread|fopen|ftp_nb_f(put|get)|ftp_get|scandir|fscanf|readgzfile|fread|proc_open|fgetc|fgetss|ftp_fput|ftp_nb_get|session_start|fwrite|gzwrite|gzopen|gzcompress|curl_multi_exec|curl_exec|eval|base64_decode|str_rot13|php_uname|file_get_contents|include|require|require_once|parse_ini_file|set|shell_exec|popen|ini_(?:get|restore)|safe_mode|phpinfo|system|exec|passthru|preg_\w+|execute)\s*[\"\(@]" \
"chain,t:none,t:urlDecodeUni,t:htmlEntityDecode,t:replaceNulls,t:replaceComments,t:compressWhiteSpace,t:lowercase,capture,auditlog,msg:'Atomicorp.com - FREE UNSUPPORTED DELAYED FEED - WAF Rules: Potentially malicious PHP code injection attempt',id:380018,rev:7,logdata:'%{TX.0}',severity:'2'"
SecRule REQUEST_URI "!(/\?q=node/[0-9]+/edit$)"
SecMarker END_PHP_CODE_INJECTION_ATTACKS_2
but I can't see how it's triggered from the previous string :-(
As a workaround I can only suggest that you could create the forms using the Wizard on a local version of Joomla! without this modsecurity setuo and then copy them over to the live site using the backup and restore icons. Not ideal but I don't' know what else to suggest.
Bob