Steps to reproduce:

1. Open page in VisualEditor's wikitext mode, and press Enter to create a new line.
2. Type a few letters.
3. Highlight something else on the page and press Control-c to copy it.
4. Click back at the end of the few letters you typed in Step #2 (as if to paste the newly copied text after it).
5. See that the text cursor isn't blinking. It may be on (and therefore visible but not blinking) or off (and therefore not visible).

Original report at https://www.mediawiki.org/wiki/Topic:Tl3uwb4lqx3x5iu8 from @Sunpriat who was running Windows 10 and the then-latest Firefox dev edition and Chrome 58.0.3013.5 dev 64.