diff --git a/wp-includes/wp-db.php b/wp-includes/wp-db.php
index 3206063a3a..11c4673074 100644
--- a/wp-includes/wp-db.php
+++ b/wp-includes/wp-db.php
@@ -1233,6 +1233,7 @@ class wpdb {
 		$query = str_replace( '"%s"', '%s', $query ); // doublequote unquoting
 		$query = preg_replace( '|(?<!%)%f|' , '%F', $query ); // Force floats to be locale unaware
 		$query = preg_replace( '|(?<!%)%s|', "'%s'", $query ); // quote the strings, avoiding escaped strings like %%s
+		$query = preg_replace( '/%(?:%|$|([^dsF]))/', '%%\\1', $query ); // escape any unescaped percents 
 		array_walk( $args, array( $this, 'escape_by_ref' ) );
 		return @vsprintf( $query, $args );
 	}
@@ -2696,7 +2697,8 @@ class wpdb {
 					}
 
 					if ( is_array( $value['length'] ) ) {
-						$queries[ $col ] = $this->prepare( "CONVERT( LEFT( CONVERT( %s USING $charset ), %.0f ) USING {$this->charset} )", $value['value'], $value['length']['length'] );
+						$length = sprintf( '%.0f', $value['length']['length'] );
+						$queries[ $col ] = $this->prepare( "CONVERT( LEFT( CONVERT( %s USING $charset ), $length ) USING {$this->charset} )", $value['value'] );
 					} else if ( 'binary' !== $charset ) {
 						// If we don't have a length, there's no need to convert binary - it will always return the same result.
 						$queries[ $col ] = $this->prepare( "CONVERT( CONVERT( %s USING $charset ) USING {$this->charset} )", $value['value'] );