demux_lavf: blacklist ffm (ffserver)

demux/demux_lavf.c

@@ -167,6 +167,8 @@ static const struct format_hack format_hacks[] = {
     BLACKLIST("bin"),
     // Useless, does not work with custom streams.
     BLACKLIST("image2"),
+    // Probably a security risk.
+    BLACKLIST("ffm"),
     // Image demuxers ("<name>_pipe" is detected explicitly)
     {"image2pipe", .image_format = true},
     {0}