In janeczku Calibre-Web 0.6.0 to 0.6.21, the edit_book_comments function is vulnerable to Cross Site Scripting (XSS) due to improper sanitization performed by the clean_string function. The vulnerability arises from the way the clean_string function handles HTML sanitization.
CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')