I hadn't updated my [https://tiddlywiki.com/ TiddlyWiki] (TW) files for a while before accepting the latest update and when trying to save from within TW today, the download failed to complete with the name I had assigned to it, rather than the one generated by FF. I found that it was possible to download the file with the name assigned by FF, then rename manually, but not sure if this qualifies as a bug. While it was previously supported, I was using the TiddlyWiki for Firefox extension but since the extension became incompatible with FF and was disabled (last year?), until today's experience, TW and FF have played nicely together.