Cannot login after disabling the authentication security mechanism

Reproduction steps:
1. Enable the Authentication security mechanism (should be enabled by default)
2. Try to login with a registered user (not admin) several times with wrong password until captcha is displayed
3. On another browsing session (another browser window) login with Admin and disable the Authentication security mechanism
4. On the same browsing session than 2, go back to the login page and try to login with Admin

Expected result:

• Since the authentication security mechanism has been disabled, you should be able to login immediately

Obtained result:

• the captcha is requested but you cannot login.