The discussion revolves around a reported bug in Composer on beta Firefox. Alankrit_Choudh shared an image of the issue, which occurs when selecting a category by topic count, and stated it’s reproducible on try.discourse.org. jomaxro suggested checking if the issue is specific to a customization or a bug. Mittineague expressed confusion about the reported issue, while dax linked to a similar bug report. claas pointed out that Firefox 50 is currently in the nightly branch and will only become stable by the end of the year, suggesting to wait until the release is at least in Developer Edition. codinghorror stated that beta browsers are not supported, and the issue should be reposted when it’s a stable release.
Note that Firefox 50 currently is the nightly branch and will only become stable by the end of the year. Therefore, if somebody reports a bug in such a version and its not reproducible otherwise (which seems not to be the case here), it is worth waiting until the release is at least in Developer Edition (aurora).