See below link. It will create a huge backlink for me if I put it on dynamically generated blog posts. Is it a blackhat SEO strategy?
<a href="http://example.com" style="display: none;">Example</a>
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It's a blackhat SEO technique if you want to manipulate search engines rankings. It can be considered as OK if the links are hidden for better user experience.
See this page on Google support for more information.
Indeed, a hidden link is not seen by visitors instead of search engines bots. It can be considered as cloaking and it's punished by search engines in general.
The answer to your question is both Yes and No. First lets start with possible reasons for using a hidden link:
So it seems like your example falls into the first of the list, trying to abuse or sneak in data. Furthermore, it seems like you know you're doing something wrong or the environment includes shadyness. Otherwise there would be no point in hiding it, right?
In the end, a hidden link is a hidden link. Its not the link's fault if you abuse it with blackhat methods. So to answer your question:
Hidden links are whitehat SEO until you abuse them. If you choose to abuse by operating a questionable environment, then yes hidden links are blackhat SEO.