Steps to reproduce:

I just opened the developer tools on my browser with F12 as the page was loading. First time I've ever experienced this, and since it asked me to file a bug report, I'm obliging. I don't expect a response back/etc. Thank you all for all that you do with this browser!

Error in Web Developer Tools:

Error: Protocol error (SecurityError): Permission denied to access property "document" on cross-origin object from: server0.conn0.watcher3 (resource://devtools/server/actors/webconsole/listeners/document-events.js:68:11)

Client Packet:

{
  "type": "watchResources",
  "resourceTypes": [
    "document-event"
  ],
  "to": "server0.conn0.watcher3"
}

Server Packet:

{
  "from": "server0.conn0.watcher3",
  "error": "SecurityError",
  "message": "Permission denied to access property \"document\" on cross-origin object",
  "fileName": "resource://devtools/server/actors/webconsole/listeners/document-events.js",
  "lineNumber": 68,
  "columnNumber": 11
}

Server Stack:

listen@resource://devtools/server/actors/webconsole/listeners/document-events.js:68:11
watch@resource://devtools/server/actors/resources/document-event.js:103:19
watchResources@resource://devtools/server/actors/resources/index.js:367:15
addOrSetSessionDataEntry@resource://devtools/server/actors/targets/session-data-processors/resources.js:19:21
addOrSetSessionDataEntry@resource://devtools/server/actors/targets/base-target-actor.js:86:23
#addOrSetSessionDataEntry@resource://devtools/server/connectors/js-process-actor/DevToolsProcessChild.sys.mjs:398:21
receiveMessage@resource://devtools/server/connectors/js-process-actor/DevToolsProcessChild.sys.mjs:323:46

Stacktrace:

onPacket/<@resource://devtools/shared/protocol/Front.js:404:31
DevTools RDP*request@resource://devtools/shared/protocol/Front.js:320:14
generateRequestMethods/</frontProto[name]@resource://devtools/shared/protocol/Front/FrontClassWithSpec.js:57:19
_startListening@resource://devtools/shared/commands/resource/resource-command.js:1082:31

Thanks a lot for the report C Myers
This looks like Bug 2005348, so I'm going to close this bug as duplicate.

But maybe you can help us investigate, do you remember which page you were on when this happened?

I do! In this case the site requires authentication, but it's Ellucian Experience, https://experience.elluciancloud.com/sdsborso/ . I was authenticated when the issue happened.