Link-shortener bypass (regression on fix for #1032610)

Report #1032610, entitled > Chained open redirects and use of Ideographic Full Stop defeat Twitter's approach to blocking links was [closed as _Resolved _ about six months ago](https://hackerone.com/reports/1032610#activity-12095285). However, a regression on the fix for the vulnerability in question seems to have occurred, and the bug is reproducible with the exact same payload. ## Impact Refer to [#1032610](https://hackerone.com/reports/1032610#user-content-impact).