From the WordPress 4.8.3 release post: WordPress versions 4.8.2 and earlier are affected by an issue where
$wpdb->prepare() can create unexpected and unsafe queries leading to potential SQL injection (SQLi). WordPress core is not directly vulnerable to this issue, but we’ve added hardening to prevent plugins and themes from accidentally causing a vulnerability. Reported by Anthony Ferrara.
This release includes a change in behaviour for the
esc_sql() function. Most developers will not be affected by this change, you can read more details in the developer note.
List of Files Revised