i use windows 8 operating system,whenever i navigate to login page of browser in internet explorer 10 or even at logon screen of operating system,i used to see eye symbol over there 


![enter image description here][1]


whenever i type the password the eye symbol occurs,when i press the eye symbol the password is visible on plain text,what's the security behind this eye,is this vulnerability on windows?


Any security behind this eye?


  [1]: https://i.sstatic.net/BCfEr.jpg