In Powerpress plugin of WordPress I’ve been confronted with this error:
Warning: curl_exec() has been disabled for security reasons
Many people suggested a hack into the functions.php of WordPress.
I find this solution not very good, since it’s most likely all gone after an update of WordPress.
After looking for a better solution in Google I found this one which suits me.
Hers is an extract of it:

Function curl_exec is disabled. What to do?

In order to eliminate this error message you need to do ONE of the following things:
Remove the curl_exec string from the disable_functions at php.ini* file
Ask your hosting provider to remove the string above if you don’t have an access to the php.ini* file
Change hosting provider which allows the running of the curl_exec function.

The best is that you run WordPress under Apache fCGI module therefore only affecting this site
and not the whole server’s PHP configuration, which could be a security risk.
Here is an example of the entry in php.ini.

Change from:
disable_functions = exec,passthru,shell_exec,system,proc_open,popen,curl_exec,curl_multi_exec,show_source,eval,posix_getpwuid
disable_functions = exec,passthru,shell_exec,system,proc_open,popen,curl_multi_exec,show_source,eval,posix_getpwuid