Pharma Hack

I have gotten this error twice now in my site’s error log…

WordPress database error Illegal mix of collations (utf8_general_ci,IMPLICIT) and (utf8mb4_unicode_520_ci,COERCIBLE) for operation 'like' for query SELECT SQL_CALC_FOUND_ROWS DISTINCT wp_posts.ID FROM wp_posts LEFT JOIN wp_term_relationships AS tr ON (wp_posts.ID = tr.object_id) LEFT JOIN wp_term_taxonomy AS tt ON (tr.term_taxonomy_id = tt.term_taxonomy_id) LEFT JOIN wp_terms AS t ON (tt.term_id = t.term_id) WHERE 1=1 AND ( ((wp_posts.post_title LIKE '%????%') OR (wp_posts.post_content LIKE '%????%') OR (wp_posts.post_excerpt LIKE '%????%') OR ( ( t.name LIKE '%????%' ) )) AND ((wp_posts.post_title LIKE '%Pills%') OR (wp_posts.post_content LIKE '%Pills%') OR (wp_posts.post_excerpt LIKE '%Pills%') OR ( ( t.name LIKE '%Pills%' ) )) AND ((wp_posts.post_title LIKE '%without%') OR (wp_posts.post_content LIKE '%without%') OR (wp_posts.post_excerpt LIKE '%without%') OR ( ( t.name LIKE '%without%' ) )) AND ((wp_posts.post_title LIKE '%prescription%') OR (wp_posts.post_content LIKE '%prescription%') OR (wp_posts.post_excerpt LIKE '%prescription%') OR ( ( t.name LIKE '%prescription%' ) )) AND ((wp_posts.post_title LIKE '%on%') OR (wp_posts.post_content LIKE '%on%') OR (wp_posts.post_excerpt LIKE '%on%') OR ( ( t.name LIKE '%on%' ) )) AND ((wp_posts.post_title LIKE '%??%') OR (wp_posts.post_content LIKE '%??%') OR (wp_posts.post_excerpt LIKE '%??%') OR ( ( t.name LIKE '%??%' ) )) AND ((wp_posts.post_title LIKE '%www.NetDoctor.store%') OR (wp_posts.post_content LIKE '%www.NetDoctor.store%') OR (wp_posts.post_excerpt LIKE '%www.NetDoctor.store%') OR ( ( t.name LIKE '%www.NetDoctor.store%' ) )) AND ((wp_posts.post_title LIKE '%??%') OR (wp_posts.post_content LIKE '%??%') OR (wp_posts.post_excerpt LIKE '%??%') OR ( ( t.name LIKE '%??%' ) )) AND ((wp_posts.post_title LIKE '%Buy%') OR (wp_posts.post_content LIKE '%Buy%') OR (wp_posts.post_excerpt LIKE '%Buy%') OR ( ( t.name LIKE '%Buy%' ) )) AND ((wp_posts.post_title LIKE '%Levitra%') OR (wp_posts.post_content LIKE '%Levitra%') OR (wp_posts.post_excerpt LIKE '%Levitra%') OR ( ( t.name LIKE '%Levitra%' ) )) AND ((wp_posts.post_title LIKE '%from%') OR (wp_posts.post_content LIKE '%from%') OR (wp_posts.post_excerpt LIKE '%from%') OR ( ( t.name LIKE '%from%' ) )) AND ((wp_posts.post_title LIKE '%$0.84/pill%') OR (wp_posts.post_content LIKE '%$0.84/pill%') OR (wp_posts.post_excerpt LIKE '%$0.84/pill%') OR ( ( t.name LIKE '%$0.84/pill%' ) )) AND ((wp_posts.post_title LIKE '%????Purchase%') OR (wp_posts.post_content LIKE '%????Purchase%') OR (wp_posts.post_excerpt LIKE '%????Purchase%') OR ( ( t.name LIKE '%????Purchase%' ) )) AND ((wp_posts.post_title LIKE '%Levitra%') OR (wp_posts.post_content LIKE '%Levitra%') OR (wp_posts.post_excerpt LIKE '%Levitra%') OR ( ( t.name LIKE '%Levitra%' ) )) AND ((wp_posts.post_title LIKE '%Canada%') OR (wp_posts.post_content LIKE '%Canada%') OR (wp_posts.post_excerpt LIKE '%Canada%') OR ( ( t.name LIKE '%Canada%' ) )) AND ((wp_posts.post_title LIKE '%-%') OR (wp_posts.post_content LIKE '%-%') OR (wp_posts.post_excerpt LIKE '%-%') OR ( ( t.name LIKE '%-%' ) )) AND ((wp_posts.post_title LIKE '%Levitra%') OR (wp_posts.post_content LIKE '%Levitra%') OR (wp_posts.post_excerpt LIKE '%Levitra%') OR ( ( t.name LIKE '%Levitra%' ) )) AND ((wp_posts.post_title LIKE '%20%') OR (wp_posts.post_content LIKE '%20%') OR (wp_posts.post_excerpt LIKE '%20%') OR ( ( t.name LIKE '%20%' ) )) AND ((wp_posts.post_title LIKE '%Mg%') OR (wp_posts.post_content LIKE '%Mg%') OR (wp_posts.post_excerpt LIKE '%Mg%') OR ( ( t.name LIKE '%Mg%' ) )) AND ((wp_posts.post_title LIKE '%Order%') OR (wp_posts.post_content LIKE '%Order%') OR (wp_posts.post_excerpt LIKE '%Order%') OR ( ( t.name LIKE '%Order%' ) )) AND ((wp_posts.post_title LIKE '%Online%') OR (wp_posts.post_content LIKE '%Online%') OR (wp_posts.post_excerpt LIKE '%Online%') OR ( ( t.name LIKE '%Online%' ) ))) AND wp_posts.post_type IN ('post', 'page') AND (wp_posts.post_status = 'publish') ORDER BY (CASE WHEN wp_posts.post_title LIKE '%???? Pills without prescription on ?? www.NetDoctor.store ?? Buy Levitra from $0.84/pill ????Purchase Levitra Canada - Levitra 20 Mg Order Online%' THEN 2 ELSE 6 END), wp_posts.post_date DESC LIMIT 0, 20 made by require('wp-blog-header.php'), wp, WP->main, WP->query_posts, WP_Query->query, WP_Query->get_posts

…and now I discover that it is a Pharm Hack.
How did something so obvious get past your plugin?
And what do I do about this now?