Just curious, because I just realized it wasn\'t an actual \"x\" (annoying how long that took to figure out).
It uses ×.
You can use the following to obtain the desired information about any character:
$ perl -Mcharnames=:full -CA -e'
printf("U+%04X %s\n", $_, charnames::viacode($_))
for unpack "W*", $ARGV[0];
' ×
U+00D7 MULTIPLICATION SIGN
If you're going to use it in HTML, you can encode it as follows:
$ perl -MHTML::Entities -CA -e'
CORE::say encode_entities($ARGV[0]);
' ×
×
Notes: