xpath injection

The d parameter appears to be vulnerable to XPath injection attacks.
The t parameter appears to be vulnerable to XPath injection attacks.
The URL path filename appears to be vulnerable to XPath injection attacks.

https://owasp.org/www-community/attacks/XPATH_Injection

Suppose we have a user authentication system on a web page that used a data file of this sort to login users. Once a username and password have been supplied the software might use XPath to look up the user:

VB:
Dim FindUserXPath as String
FindUserXPath = "//Employee[UserName/text()='" & Request("Username") & "' And
        Password/text()='" & Request("Password") & "']"

C#:
String FindUserXPath;
FindUserXPath = "//Employee[UserName/text()='" + Request("Username") + "' And
        Password/text()='" + Request("Password") + "']";

With a normal username and password this XPath would work, but an attacker may send a bad username and password and get an XML node selected without knowing the username or password, like this:

Username: blah' or 1=1 or 'a'='a
Password: blah

FindUserXPath becomes //Employee[UserName/text()='blah' or 1=1 or
        'a'='a' And Password/text()='blah']

Logically this is equivalent to:
        //Employee[(UserName/text()='blah' or 1=1) or
        ('a'='a' And Password/text()='blah')]

In this case, only the first part of the XPath needs to be true. The password part becomes irrelevant, and the UserName part will match ALL employees because of the “1=1” part.