Hyungseok Han contributed to the google/oss-fuzz repository by enhancing the reliability of the PySecSan Regex DoS detector. He focused on improving vulnerability detection by correcting the hook installation for re.pattern.findall, shifting from a pre-execution to a post-execution hook. This adjustment ensured that the detector accurately identified Regex DoS vulnerabilities, reducing missed cases and false negatives across fuzzing targets. Han applied his expertise in Python, bug fixing, and security analysis to stabilize the detection pipeline. His work demonstrated a deep understanding of code analysis and security, laying the groundwork for broader coverage and more robust vulnerability detection in future releases.