CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PATH_AS_IS, long leaveit);
This instructs libcurl to NOT squash sequences of "/../" or "/./" that may exist in the URL's path part and that is supposed to be removed according to RFC 3986 section 5.2.4.
Some server implementations are known to (erroneously) require the dot dot sequences to remain in the path and some clients want to pass these on in order to try out server implementations.
By default libcurl will merge such sequences before using the path.
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/../../etc/password");
curl_easy_setopt(curl, CURLOPT_PATH_AS_IS, 1L);
curl_easy_perform(curl);
}