Seeing Firefox error: Permission denied to access property "target"

[joshma]

This looks like a bug, and I currently suspect some odd interaction between raven and iframes/plugins.

What is the current behavior?
Ironically, this is captured by raven, but the stack shows it's an error in raven:

Error: Permission denied to access property "target"
  at _before(~/raven-js/src/raven.js:643:0)
  at _before(~/raven-js/src/raven.js:257:0)

The code looks like this:

_breadcrumbEventHandler: function(evtName) {
    ...
    var elem = evt.target;
}

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/Property_access_denied suggests it could be due to an iframe and cross-origin issues. We do have some iframe embedded, although I haven't been able to reproduce the error.

My current theory is that "some combination of events" is leading to raven's breadcrumb handlers attempting to capture that event, which then errors when accessing evt.target.

It happens once every few weeks for us, all on Firefox, across a range of operating systems.

What is the expected behavior?
It shouldn't error. :)

Currently on raven 3.0.4.

[benvinegar]

My guess is that there is an event handler that would similarly throw "permission denied to access property", but it's failing inside Raven first.

The simplest thing we can do is just try/catch accessing this and bail out if there's a failure, but I'd really love if we could recreate the scenario first (e.g. on jsbin).

[benvinegar]

See #857