def get_valid_filename(value, replace_whitespace=True, chars=128):
    """
    Returns the given string converted to a string that can be used for a clean
    filename. Limits num characters to 128 max.
    """
    if value[-1:] == u'.':
        value = value[:-1]+u'_'
    value = value.replace("/", "_").replace(":", "_").strip('\0')
    if use_unidecode:
        if config.config_unicode_filename:
            value = (unidecode.unidecode(value))
    else:
        value = value.replace(u'§', u'SS')
        value = value.replace(u'ß', u'ss')
        value = unicodedata.normalize('NFKD', value)
        re_slugify = re.compile(r'[\W\s-]', re.UNICODE)
        value = re_slugify.sub('', value)
    if replace_whitespace:
        #  *+:\"/<>? are replaced by _
        value = re.sub(r'[*+:\\\"/<>?]+', u'_', value, flags=re.U)
        # pipe has to be replaced with comma
        value = re.sub(r'[|]+', u',', value, flags=re.U)
    value = value[:chars].strip()
    if not value:
        raise ValueError("Filename cannot be empty")
    return value
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.