Curly braces in link preview title shown as HTML entities about mastodon HOT 1 CLOSED

Reproduced this on latest main code in addition to 4.2.8. The cause of this issue is the use of the default decoding flavor from HTMLEntitites here: https://github.com/mastodon/mastodon/blob/main/app/lib/link_details_extractor.rb#L285 .

The curly bracket entity codes (among others) are not included in the XHTML1 or HTML4 specs, only the entity numbers for them are. Thus a site with { (one of two entity numbers for left curly bracket) renders appropriately but { does not.

HTMLEntities supports an expanded set of entity names from a variety of public domain sources, as detailed here. Simply instantiating the HTMLEntities decoder with :expanded instead of the default flavor should resolve this issue for any entities whose names are not in the XHTML1 or HTML4 specs.

Do note that, because link details are extracted and stored on post, that this will not retroactively fix the display for already posted links. If that same link is then posted again it will fix for all cards since the details are stored based on the link name and a fresh post would trigger a new extraction.

from mastodon.