Was. Sometimes even a good site (or an ad server they use) gets hacked, and so a page that was fine yesterday can be bad today - and if they clean it up, good next week.
Yandex is a major Russian search engine. As with other search engines, if they find malware while indexing a site, they report it. The site's owners should be able to contact Yandex and find out what they saw, then clean it up and ask Yandex to scan them again.