I found a bug in the index filters - it probably doesn't affect most of you so you only really need to apply if you think its relevant. And this is only relevant if your version of zen cart is from when the index_filters directory came into existence.
One example would be if you're using the whats_new sidebox - the sidebox itself will work initially but if you click [more] it will then not filter out products from your other sites.
To each of these files in includes/index_filters/
default_filter.php
music_genre_filter.php
record_company_filter.php
find the section that looks like -
PHP Code:
$listing_sql .= ' ' . $where_str . ' ' . $order_by;
// optional Product List Filter
and change it to -
PHP Code:
$listing_sql .= ' ' . $where_str . ' ' . $order_by;
//bof: multisite
$listing_sql = cat_filter($listing_sql);
//eof: multisite
// optional Product List Filter