RT-AC86U_384.18_0: weblogin no longer possible

[amigohd]

I can't login by webinterface or ssh anymore.
There is a captcha needed (never seen this before). Username, password (and captcha) are correct, but I get an error "Invalid username or password".
Tried to reboot, still the same. All is working fine, except the login.

Anyone has an idea what is going on? How can I login again?

 

[amigohd]

i did reset the router and loaded my backup configs. everything fine again.

 

[RMerlin]

This will happen if you switch from a very recent RT-AC86U firmware to an older one. The password is now encrypted, so you can't downgrade without doing a factory default reset.

The captcha will appear after a number of invalid password attempts.