Vendor notified at and partial patch:
https://forums.xmbforum.com/viewthread.php?tid=754523

firstly the input validation at xmb.php:

foreach ($global as $num => $array) {
if (is_array($array)) {
extract($array, EXTR_OVERWRITE);
}
}

this should put to not overwrite any variables cause
it overwrite server set variables too. this creates problems
when user submits a additional field in form:

<input type="text" name="_SERVER[REMOTE_ADDR]" value="555.555.555.555">


secondly there is a case of sql injection in include/u2u.inc.php
line ~491:
Code:

$in = '';
foreach ( $u2u_select as $value ) {
if ( $GLOBALS['type'.$value] != 'outgoing' ) {
$in .= ( empty( $in ) ) ? "$value" : ",$value";
}
}
...
$db->query( "UPDATE $table_u2u SET readstatus='no' WHERE u2uid IN($in) AND owner='$self[username]'" );

the variable $in is not actually validated and could and will cause problems if not fixed.

Greets #rainbowcrack and https://www.waraxe.us