Initial report.

Steps to reproduce:

1. Copy the URL to an article on English Wikipedia (https://en.wikipedia.org/wiki/Foo)
2. go to another wiki than English Wikipedia
3. create a link with the URL you have copyied (labelled "Test" on my example)

Expectation: [https://en.wikipedia.org/wiki/Foo Test] or [[:en:Foo|Test]]
Reality: [[Wikipedia:Foo|Test]]

Tested and reproduced on French Wikipedia and on Catalan Wikipedia. This bug breaks some links by creating links to the Wikipedia: namespace.

If I create on English Wikipedia a link to a French Wikipedia article, the link is rendered well.