SSI Security Threat(s)?

[Firefox Wins]

The most secure way to operate is to disallow all SSI processing... ~Source

With 'private' (i.e. single-user not shared) hosting on a VPS or Dedi is using SSI less risky?*
*since secure file perms for individual users are not an issue?

(or try another way to ask)

If, for example, regarding this code:

PHP Code:

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<?php // This section is not a SSI... // This section is not a SSI... require_once("./inc/local/local_vars.php"); define('IN_MYBB', 1); require_once './global.php'; if($mybb->user['uid'] == 1) { } else { error_no_permission(); } $command = "$rsyncpaths1"; system($command); ?>

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'System', 'exec', etc. are often considered highly dangerous.
In the above code, no user input can effect the included $var(s) + only Super-admin can activate the little script, so...

1) Based on the info given:
That usage of 'system' commands is "safe", correct?

2) Also curious about SSI in general, should it be considered highly risky?
Thanks to anyone w/ security experience...