- On enwiki, create a page containing this invalid link: http://ABCD:0000:0000:0000:0000:0000:0000:0000
- With a non-autoconfirmed account, add more text to the page. Do not add any more links.
The expected result is no CAPTCHA. The actual result is a CAPTCHA, even though no new external links were added.
Example: this edit required a CAPTCHA to save.
If the URL is instead formatted correctly, as http://[ABCD:0000:0000:0000:0000:0000:0000:0000], other edits do not trigger the CAPTCHA.
Example: this edit required no CAPTCHA, as expected.