Permission denied to call method Location.toString

For a while I've been noticing seemingly random errors popping up on some of my websites. It hadn't happened on my blog here, but other sites caused this error to appear in Firebug:

Permission denied to call method Location.toString

No file name, no line number, no indication where the error occurs or why. Upon further investigation I discovered that it only happened when there was Google Adsense or other remote flash media involved.

As it turns out, the error is caused by a change in Flash's security policies between versions 9.0.115.0 and 9.0.124.0 — this is both good and bad news. I'm glad to learn that it's not an error anywhere in my code, but it's unfortunate that there's nothing I can do to get rid of the error, short of removing Adsense from those pages.

var tags = [flash and actionscript, personal];