A Regular Expression Denial of Service (ReDoS) vulnerability exists in the latest version of gaizhenbiao/chuanhuchatgpt. The vulnerability is located in the filter_history function within the utils.py module. This function takes a user-provided keyword and attempts to match it against chat history filenames using a regular expression search. Due to the lack of sanitization or validation of the keyword parameter, an attacker can inject a specially crafted regular expression, leading to a denial of service condition. This can cause severe degradation of service performance and potential system unavailability.