Hi, Since upgrading to El Capitan when logging in after the system has gone into sleep mode, the login password field starts to auto populate with a lot more figures than in our login password.
Yes! I'm having the exact same problem with my iMac. The field will sometimes just auto populate to the end and the only solution is to force a shutdown and restart. Never happened until the upgrade.
I had this same issue on my MacBook Air with Yosemite but much less frequently. Interestingly, it is fine with El Capitan.