What are these requests to the base of the wordpress site?

Question

WordPress

SELECT SQL_CALC_FOUND_ROWS  mzd_posts.ID FROM mzd_posts  WHERE 1=1  AND (((mzd_posts.post_title LIKE '%301%') OR (mzd_posts.post_excerpt LIKE '%301%') OR (mzd_posts.post_content LIKE '%301%')))  AND (mzd_posts.post_password = '')  AND mzd_posts.post_type IN ('post', 'page', 'attachment') AND (mzd_posts.post_status = 'publish')  ORDER BY mzd_posts.post_title LIKE '%301%' DESC, mzd_posts.post_date DESC LIMIT 0, 10

Many of these queries run for a very long time and crash mysql in the end.
I did not find them in the site code.
Where do they come from?