I read that it was related to text-boxes so I figured that could be a potentially hidden culprit. I haven't heard of web pages crashing due to embedded text but if so then I retract my hypothesis.
2nd Sentence of the article says text box but not sure what "other places" are:
"Basically, if you put this string in any system text box (and other places), it crashes that process."
From the article's source article: "iMessages, [...] Facebook Messenger, WhatsApp, Gmail, and Outlook for iOS [...] can become disabled once a message is received". "It might be difficult to fix and delete the problem message".
From the article: "I’ve been testing it by copy-pasting characters into Spotlight so I don’t end up crashing my browser". "I can cause this crash to happen more reliably in browsers by clicking on the string".
So, not text-box specific and happening on display for a wide variety of applications, including web pages.
