Opera 9.5 (at least this version) doesn't like null username being sent into XMLHttpRequest, this creates a login prompt in Opera, so jQuery should circumvent this

[kai@…]

By doing like this

if(s.username == null) { xml.open(s.type,s.url,s.async/*,s.username,s.password*/); } else { xml.open(s.type,s.url,s.async,s.username,s.password); }

The bug happens when you run getJSON or getScript with Opera 9.5, on a non password protected machine. In the IIS log I see the username "undefined" appear.

[flesler]

Fixed at [5604].

[kai@…]

actually this seems fixed in 1.2.4 according to the release notes, but I checked, and this fix is NOT included in 1.2.4.

[greylurk]

Just as a note, this bug also affects Firefox 1.0 (Gecko 20041107) but since it's been fixed in 1.2.6, it doesn't really matter.

According to the  FireFox documentation the default username and password are blank strings, not null. A better long term fix may be to set the default username and password to "" instead of null, rather than using an if to determine whether the username is present.