If you download the 2023-09-15 firmware today, the .zip files are 4k larger than they were when originally released. For example OpenGD77.zip was 212k, but now it's 216k, at the same location, and OpenDM1701.zip was 224k, but now it's 228k. The change happened on Thursday.
downloads/MDUV380_DM1701/Firmware/ad235 ... eb02229fa/ for example, but I don't have anything I can point to, to show that it was 4k smaller before. What I have is a notification from Wachete, which I use to detect when there's a new release.
I wondered briefly if they'd been tampered with. Infected, perhaps. The modification timestamps haven't changed, which is unusual if they were modified intentionally.
I suppose it's also possible that the web server was updated and now accounts for size differently, or it could be using the size on disk instead of the actual or apparent size of the files, and something in the filesystem has changed.
I'll have to see if I have a copy of the file from before the size (or the way is reported by the web server) changed.