Marshall Epper enhanced domain extraction capabilities in the gchq/CyberChef repository by implementing support for underscores in DMARC and DKIM domains. He introduced a new regular expression, DMARC_DOMAIN_REGEX, and exposed it as an optional argument within the ExtractDomains operation, allowing for more comprehensive domain discovery in security workflows. This JavaScript-based solution addressed a gap in existing domain extraction logic, reducing the need for manual post-processing and improving the accuracy of automated cybersecurity operations. Marshall’s work demonstrated a focused application of regular expressions and domain extraction techniques, delivering a targeted feature with clear utility for security practitioners and automation pipelines.