To mitigate JWT signature vulnerabilities, it is crucial to use standardized JWT libraries, properly set them up and verify signature and expiration of JWT tokens before any operation.  

It's also crucial to securely store the `secret key` as it can render any security mitigations useless if it gets leaked.

=== "Kotlin"
	```kotlin
	import io.jsonwebtoken.JwtException
	import io.jsonwebtoken.Jwts
	import io.jsonwebtoken.SignatureAlgorithm
	import io.jsonwebtoken.security.Keys
	import java.security.Key
	
	// Secure JWT validation
	fun validateJwt(token: String, secretKey: Key): Boolean {
	    try {
	        Jwts.parserBuilder()
	            .setSigningKey(secretKey)
	            .build()
	            .parseClaimsJws(token)
	        return true // Token is considered valid
	    } catch (e: JwtException) {
	        return false // Token validation failed
	    }
	}
	
	fun main() {
	    val token = "eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwiaWF0IjoxNTE2MjM5MDIyfQ.4x6fOGYwfFYIQgZepgK1AnbDDr2-TvAp6im0kKk52Es"
	    val secretKey = Keys.secretKeyFor(SignatureAlgorithm.HS256) // Generate a secure secret key
	
	    val isValid = validateJwt(token, secretKey)
	    if (isValid) {
	        println("Token is valid")
	        // Proceed with further processing
	    } else {
	        println("Token validation failed")
	        // Handle invalid token
	    }
	}
	```


In this example, the validateJwt function takes a JWT token and a secure secret key as input. The `Keys.secretKeyFor` method from the jjwt library is used to generate a secure secret key using the `HS256` algorithm.

The function attempts to validate the token by parsing its claims using the `Jwts.parserBuilder()` method. The `setSigningKey` method is used to set the secure secret key for signature verification. This ensures that the token's signature is validated securely.

If the token is successfully parsed without any exceptions, it is considered valid. Otherwise, if a `JwtException` occurs during the parsing process, the token validation fails.

By using a secure secret key and following best practices for key management, such as generating keys with sufficient randomness and protecting them from unauthorized access, you can enhance the security of your JWT implementation.