Getting Error at the Top of My Website Homepage

As the title says. This is at the top of my website:

Warning: DOMDocument::loadHTML(): Invalid char in CDATA 0x3 in Entity, line: 4 in /home/fixcoffee/fixcoffee.net/wp-content/themes/upfront/elements/upfront-text/lib/upfront_text.php on line 21

What does it mean? What can I do?