I have looked into this further and I have a theory that user-added toolbars are the cause of the errors. I would like some confirmation that this could be the cause.
Here is a more complete description:
Here are the most common example of those "foreign URLs:"
I am already aware that cloudfront is an Amazon service. There are numerous such errors starting back on 26-Jun-11. There is a pattern in which typically a dozen or two such errors occur in a short time from, all from a single IP address. Then there is a large gap of time. This makes me wonder if it could be something that a user does on their browser to use some facility of Amazon for example. Is your team aware of anything like this?
The "babylonConduit" also occurred from a single IP over a short period of time, which also seems to imply something the user is doing.
More miscellaneous examples:
/searchqutoolbar/content/toolbar.xul (seems more like this would be a Chrome issue, something that is in Chrome, but causes an error report)
I want to stress again that we do not use any of the above in our site, so they are coming from elsewhere.
[edited by: tedster at 12:25 am (utc) on Jan 4, 2012]
[edit reason] de-link the URLs so they can be read [/edit]