https://plxqmjeom0e7pd4c-zippykid.netdna-ssl.com/w

Last month, documents released by the DOJ indicated that not only was the dossier a major component of the warrant applications, but also that an article by Yahoo! News’s Michael Isikoff, allegedly a product of circular reporting from Christopher Steele, was included as a source.

So we have a planted news article and a fake dossier used to get the FISA warrant.
That warrant was obtained illegally and it makes Mueller's investigation illegal!