valid_filetype(char_u *val)
{
    char_u *s;

    for (s = val; *s != NUL; ++s)
	if (!ASCII_ISALNUM(*s) && vim_strchr((char_u *)".-_", *s) == NULL)
	    return FALSE;
    return TRUE;
}
The product receives input or data, but it does
        not validate or incorrectly validates that the input has the
        properties that are required to process the data safely and
        correctly.