From the release of 4.8.3:
"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."
Yikes, SQL injections are a bad thing. SQL injections can allow for nefarious SQL statements to be inserted into an entry field for execution. One example of this is to allow an attacker to dump your database contents. It is always advised that security releases are applied as soon as possible.
The official release notes: WordPress 4.8.3 Released