Let's ask the Big G about WebAssembly
Let's inspect the source code http://mercury.picoctf.net:26318/index.html
Let' see what is in the JIFxzHyW8W file http://mercury.picoctf.net:26318/JIFxzHyW8W
flag:picoCTF{8857462f9e30faae4d037e5e25fee1ce}
If this write-up is riddled with typos, blame the sleep deprivation from all-night hacking.