Hi All,
someone know how to force K2 2.5.6 installed over joomla 2.5.4 to use the FTP upload method inherited into Joomla?

Please, don't tell me that it's a trivial problem:
1) if i can't do this, i'm forced to permit to frontend user to upload attachments as the apache user. this means that apache user can have the ability to write over the disk, read it and perhaps execute what they upload. this is a major security leak, and one of the motivation that pull me to use Joomla Instead of WordPress
2) if you search around in google for "wordpress problem" you can see how many ISP and hoster doesn't accept a solution with apache user that write over disk. this isn't fool, they have a lot of good reason for it.

so, we use joomla also because the FTP function increase a lot our security, we install our loved community manager plugin K2... and we have to discover that K2 doesn't use FTP also if it's enabled into Joomla, and requires permission like 775 to correctly managing upload?

i can only hope that is is something that i don't know into new 2.5 K2 release configuration...

someone can help me?

When installing Joomla, and you create a mysql database and user to begin with with phpmyadmin or similar, doens't a unix user get created? If you set your server to use fastcgi mode, it will not run as apache but as the same user as the mysql user. If you use that user for the Joomla FTP wont that solve your problem?