I am also facing the same issue. As other have mentioned, this issue can only be fixed on Shopify’s end and should be fixed as soon as possible.
Everyone should note that this issue does have a negative impact on SEO. Once the spam links started in December 2022, my entire website stopped being shown by Bing search. (As of now, Google search seems unaffected.)
Not a single page of my website is shown anymore on Bing (I cannot even search for my homepage). I used to get around 1000 organic clicks from Bing per month, but now I am getting absolutely 0.
I have implemented the solutions mentioned in this thread and the other thread. A “noindex” tag was added to all the vendor pages. I used the Removal tool to block all “URL/collections/vendors?q=” spam pages.
Although I am speaking for myself, I am sure others have worked very hard for their SEO over many years. It is deeply concerning that all this work is put into jeopardy for something that should easily be fixable by Shopify.
I went from 141 indexed pages to 364,235 indexed pages over the span of one week. Since implementing the “noindex” solution, over 2 million pages have been blocked from indexing.
I can only assume others being hit by this issue have millions of spam pages indexed if they are not quickly made aware of the problem.
I sincerely hope Shopify manages to fix vendor pages to put an end to this issue. We can only try to mitigate the damage as best as we can until Shopify intervenes.