Why are email subject fields interpreted as HTML?

I forgot to check earlier, but the "View Full Header" option (in the "More" menu, under the message body) also gets it right: all three numeric encodings are shown as plain text (with the ampersand through semicolon showing), just like the Mail Basic page.

Also, the Inbox listing of the messages shows the three encodings correctly, unlike the message when one opens it.

Fortunately it does not appear that

... less than is mishandled in any of the above places, so it is not as likely that this bug could be used for an exploit (I think).

If anyone's paying attention, the less than symbol (you know, left angle bracket, the HTML tag lead-in character) caused my previous edit here to get truncated, so I guess Answers is not very robust against user text either. But that's a whole other topic.

Hi Darcy, thanks for the link to the uservoice report but it is the flip side of the coin -- it tells of apostrophes typed to Yahoo Mail's compose dialog being converted to HTML character references in the sent mail.

What I'm reporting is those references in mail received being converted back to apostrophes. The bug I'm reporting kind of hides the bug they are tracking, but two wrongs don't make a right!

I've added it to the Feedback forum now:

http://yahoo.uservoice.com/forums/210695/suggestio...