Hi all,
I have just found a way to fix this. The @CaptchaResponse annotation has to be extended, adding 2 new parameters. When the 2 new parameters are added, Hibernate-Validator 4.2 stops complaining about missing group.

This is the class in Seam2.3.0.Beta2

org.jboss.seam.captcha.CaptchaResponse.java
package org.jboss.seam.captcha;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import javax.validation.Constraint;

@Retention(RetentionPolicy.RUNTIME)
@Documented
@Target(ElementType.METHOD)
@Constraint(validatedBy=CaptchaResponseValidator.class)
public @interface CaptchaResponse 
{
   String message() default "incorrect response";
}

The class must be extended with 2 new methods "groups" and "payload", as following:

CaptchaResponseFixed.java
public @interface CaptchaResponse 
{
   String message() default "incorrect response";
   Class<?>[] groups() default {};
   Class<?>[] payload() default {};
}

With the new methods hibernate validator stops complaining about missing groups.
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