Created attachment 267451 [details]
Shows the bug when selecting contents.
1. Open the attached iframe-selection-test.html
2. Scroll down to iframe.
3. Try to select contents inside the iframe.
4. Observe that the parent page is scrolled down.
This happens in Safari 9.0.2 and the latest nightly build (r194132).
This is a major regression and there is no way for us to prevent this from happening from the JS side. It affects editors like TinyMCE but also any iframe on pages with scroll.
This is a duplicate of https://bugs.webkit.org/show_bug.cgi?id=152541 and marked as RESOLVED FIXED.