This web application is configured to use default or weak credentials.
Acunetix was able to guess the credentials required to access this page. A weak password is short, common, a system default, or something that could be rapidly guessed by executing a brute force attack using a subset of all possible passwords, such as words in the dictionary, proper names, words based on the user name or common variations on these themes.
Change credentials for this web application. Enforce a strong password policy. Don't permit weak passwords or passwords based on dictionary words.