SQL injection vulnerability (possible patch)

I was checking my PHP error log and got the following:

WordPress database error You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ‘) LIMIT 5’ at line 1 for query SELECT DISTINCT ID FROM wp_60_posts WHERE MATCH (post_title,post_content) AGAINST (‘

— huge multiline post content stuff here —

‘) AND post_date <= ‘2013-11-18 11:49:33’ AND post_date >= ‘2010-11-20 11:49:33’ AND post_status = ‘publish’ AND ID != 20787 AND ( ) LIMIT 5 made by
require(‘wp-blog-header.php’),
require_once(‘wp-includes/template-loader.php’),
include(‘/themes/my_theme/single.php’),
the_content,
apply_filters(‘the_content’),
call_user_func_array,
ald_crp_content,
ald_crp,
get_crp_posts

I checked your plugin and found this block of code:

$sql = "SELECT DISTINCT ID "
. " FROM ".$wpdb->posts." WHERE "
. "MATCH (post_title,post_content) AGAINST ('".$stuff."') "
. "AND post_date <= '".$now."' "
. "AND post_date >= '".$current_date."' "
. "AND post_status = 'publish' "
. "AND ID != ".$post->ID." ";
if ($crp_settings['exclude_post_ids']!='') $sql .= "AND ID NOT IN (".$crp_settings['exclude_post_ids'].") ";
$sql .= "AND ( ";
$multiple = false;
foreach ($post_types as $post_type) {
	if ( $multiple ) $sql .= ' OR ';
	$sql .= " post_type = '".$post_type."' ";
	$multiple = true;
}
$sql .=" ) ";
$sql .= "LIMIT ".$limit;

$results = $wpdb->get_results($sql);

This is bad! Never just drop your content into the SQL like that! Your addslashes() won’t always help you. This is an SQL injection vulnerability. Take a look at the wpdb documentation.

Your query should look like the following (completely untested):

$args = array(
	$stuff,
	$now,
	$current_date,
	'publish',
	$post->ID,
);
$sql = "
	SELECT DISTINCT ID
	FROM ".$wpdb->posts."
	WHERE MATCH (post_title,post_content) AGAINST (%s)
	AND post_date < %s
	AND post_date >= %s
	AND post_status = %s
	AND ID != %d
";
// I really hope the below is already sanitized! If not do something like
// implode(',', array_map('intval', array_map('trim', explode(",", $crp_settings['exclude_post_ids']))))
// but over multiple lines to avoid PHP reference warnings
if ($crp_settings['exclude_post_ids']!='')
	$sql .= "AND ID NOT IN (".$crp_settings['exclude_post_ids'].") ";
$sql .= " AND (";
foreach ($post_types as $post_type) {
	if ( $multiple ) $sql .= ' OR ';
	$sql .= " post_type = '%s";
	$multiple = true;

	$args[] = $post_type;
}
$args[] = $limit;
$sq .= " ) LIMIT %d";

$results = $wpdb->query($wpdb->prepare($sql, $args));

http://wordpress.org/plugins/contextual-related-posts/