Again a hidden flag.
Challenge Description
As Hidden Two came out the same time as HV19.07 Santa Rider I thought it might be again of the challenge that also came out that day like before with Hidden One. I thought it was odd, that there was a download for a zip containing the video of day 7 while the video was also just embedded into the page. No need for download. So I thought, as the file names seem randomly generated, maybe the video was put inside a zip file, to assure that the file name of the video – which is 3DULK2N7DcpXFg8qGo9Z9qEQqvaEDpUCBB1v – stays the same.
Decoding this using Base58 reveals the flag HV19{Dont_confuse_0_and_O}.