As the global ecological and environmental problems become more and more serious, the concept of green finance and sustainable development has been advocated by more and more domestic and foreign experts, scholars and investors, and the Environmental Responsibility, Social Responsibility, and Corporate Governance (ESG) rating has gradually become a hotspot of attention. ESG is a kind of investment concept and a comprehensive assessment criterion of corporate performance for systematic evaluation of enterprises, and it has become an important indicator of the ability of measuring the sustainable development of enterprises. It has become an important indicator of corporate sustainable development capability. In this paper, we investigate the relationship between ESG ratings and cumulative abnormal returns of listed companies’ stocks under the impact of sudden risk events. The outbreak of the New Crown epidemic as an exogenous risk event provides an opportunity for this paper. This paper examines the role of firms’ ESG ratings and the three sub-dimensions of ratings on the cumulative abnormal returns of listed firms’ stocks during the New Crown Epidemic outbreak and verifies the role of ESG ratings on firms in times of crisis. The final regression results prove that under the impact of sudden exogenous risk events, listed firms’ ESG ratings have a positive effect on the cumulative abnormal stock returns during the event window. Finally, this paper provides recommendations to help firms and investors prevent and mitigate risks.

This study provides a comparative analysis of Environmental, Social, and Governance (ESG) ratings methodologies and explores the potential of eXtensible Business Reporting Language (XBRL) to enhance transparency and comparability in ESG reporting. Evaluating ratings from different agencies, the research identifies significant methodological inconsistencies that lead to conflicting information for investors and stakeholders. Statistical tests and adjusted rating scales confirm substantial divergence in ESG scores, primarily due to differing data categories and indicators used by rating firms. Using a sample of 265 European companies, the study demonstrates that individual ESG agencies report markedly different ratings for the same firms, which can mislead stakeholders. It proposes that XBRL based reporting can mitigate these inconsistencies by providing a standardized framework for data collection and reporting. XBRL enables accurate and efficient data collection, reducing human error and enhancing the transparency of ESG reports. The findings advocate for integrating XBRL in ESG reporting to achieve higher levels of comparability and reliability. The study calls for greater regulatory oversight and the adoption of standardized taxonomies in ESG reporting to ensure consistent and comparable data across sectors and jurisdictions. Despite challenges like the lack of a standardized taxonomy and inconsistent adoption, the research contends that XBRL can significantly improve the reliability of ESG ratings. In conclusion, this study suggests that standardizing ESG data through XBRL could provide a viable solution to the unreliability of current ESG rating scales, supporting sustainable business practices and informed decision making by investors.