I built you an example using my BubbleEssentials plugin.
Hope this helps.
Editor | Demo (Parent page with the iFrame and the links inside of it pointing to the iFrames parent origin url)
The index page is the iFrame content, the “parent” page is the parent.
The resulting javascript was pretty advanced as I queried all links within your frame, then applied the new properties.
You’ll likely need to modify/tweak to work to your advantage.
When you’re using version-test mode, make sure you enable devMode (inside index’s Run Javascript workflow.
What is my plugin doing?
Adding custom css + javascript to the pages.
NOTE: This will only work on things you wrap or use the “Link” element via Bubble Editor. Also, not sure whether or not this will work if the origin is not the same as the parent origin. If it doesn’t, just change a variable on the script to add your own custom origin url instead.