@glimfeather, do you use Zotero by any chance?
I noticed that these issues on Discourse sites did not happen in a private window, so I started to suspect extensions. After bisecting those, it seems the Zotero Connector extension is the culprit for me.
This Zotero forum thread confirms they’ve had some recent issue that caused errors on various sites.
I was able to get things working again with the following steps:
- Disable the Zotero Connector extension in Firefox
- Restart the Zotero desktop app
- Enable the connector extension again
- Refresh any Discourse tabs that were already loaded