It appears that the markdown export process spoils URLs that conain the
char '=' by wrongly replacing it with '%3D'.

This happens with org-links [[url][some_text]], but not with plain URLs.

I took a quick look at the defun 'org-md-link' and could see that the org-link
URLs are already spoiled when they get retrieved as 'raw-path' by the line:

	  (t (let* ((raw-path (org-element-property :path link))

So, I got stuck there.

Hoping that it's easy to resolve this bug for people more familier with the
new exporter.

All best,
mc

-- 
Fetch my gnupg key:
gpg --keyserver pgp.mit.edu --recv-keys 7E3CA33F