This seems to be a simple fix: use HTTP::Message->decoded_content in place of $var{content} = $response->content; on line 368 of WebGUI/Asset/Wobject/HttpProxy.pm.

This should convert any weird character encodings into Perl's Unicode representations, which should fix it.

I, of course, don't know a good way to reproduce this, so if you could make the following change:

Line 369 of WebGUI/Asset/Wobject/HttpProxy.pm
$var{content} = $response->content;

-- Should instead be 

$var{content} = $response->decoded_content || $response->content; 

And then if you restart apache, clear your cache, and test, it should work.

Let me know the results.

If I get the appropriate approval, this may be added to 7.3.9. 

I ran into this bug too (in WebGUI 7.4.27), but in my case it seemed to be that the HTTPProxy.pm module wasn't setting the Content-Type header like the rest of WebGUI does. So it was falling back on Apache's default, which was ISO-8859-1 in my case.

When I changed my Apache default charset to UTF-8, all was well. I needed to make that change anyway, so I'm all set. But it seems like there's still a bug here. 

I don't have a good way to test this either, but I'm making the change Doug mentioned as it is the correct behavior.

Could you please test this in the next release or describe fully a way to test this?