For some reason the update system is not able to parse the xml despite it's well constructed (it has been used by hundred of other customers).
Anyway you should be able to manually update it...
Did you try disabling the firewall before updating? Maybe there is some setting preventing communication or uploading certain file types. If that doesn't solve the issue please send me administrative credentials to access the backend (use the email from which you receive forum notifications).
Hi Jose, thanks for the fast reply.
I tried to manually update but he give an error. The message say simply "error" without any further explanation.
And now, after i checked, the version is correct 3.1.7. But I do not know if something went wrong in the update process
It's really odd you can't update the extension manually; the only way to know what's happening is checking the error_log file from your (apache) server.
Anyway you can check if everything is fine checking all component's version from Extensions -> Manage looking for "security" into the search box (the installer remains in 3.1.6 version, but this is not an error):