xauth_valid_string(const char *s)
{
	size_t i;

	for (i = 0; s[i] != '\0'; i++) {
		if (!isalnum((u_char)s[i]) &&
		    s[i] != '.' && s[i] != ':' && s[i] != '/' &&
		    s[i] != '-' && s[i] != '_')
		return 0;
	}
	return 1;
}

This category addresses vulnerabilities caused by flawed access control mechanisms, where incorrect permission settings allow unauthorized users to access restricted resources.