What Does ?, &, or _RDR Mean in a URL?

May 16, 2022

There are lots of times that you may see the string _rdr in a Facebook URL. Often it follows either a ? (question mark) or an & (ampersand), such as in facebook[dot]com/gettingstarted/rdr or http://www.facebook.com/gettingstarted/?step=friend_suggestions&_rdr. But what do they mean? Read on.

The first thing to understand is that, generally speaking, either a ? or a & are not part of the web address – they are things that get added on in order to provide the website’s server with additional information.

The ? can be thought of as telling the website “Attention, website server! The following data is for you to process.”

So, for example, if you do a search on our site, through the search box, for the term ‘monkey’, the results will be at this URL:

https://www.theinternetpatrol.com/?s=monkey

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In this example, the ? is telling theinternetpatrol.com server “Attention, server! This person is searching for articles containing the term ‘monkey’.”

The “s=” on our system tells our server that the term following the “s=” is the search term; the ? has alerted our server to the fact that there is information to process – that information being the “s=monkey”.

The & is how you string together additional information.

For example, you might see in a payment URL (such as a Paypal link):

paymentprovider[dot]com/cgi-bin/webscr?email=test@example.com&shipping=no&currency_code=USD

In this example, the data to the right of the ? is telling the payment processor that the customer’s email address is test@example.com, that there is no shipping, and that the customer is paying in USD (U.S. dollars).

This brings us to some of the most confusing Facebook URLs of all time (at least judging by the searches we get): what do “?_rdr” and “&_rdr”, such as in https://m.facebook.com/gettingstarted/?_rdr or https://m facebook com/gettingstarted/?step=friend_suggestions&_rdr, in a Facebook URL mean?

With your newfound understanding of ? and &, you can see that the _rdr is always following either a ? or a &, which means that it is data being passed to and collected by Facebook, or somehow used by the Facebook server.

Some have guessed that the “rdr” stands for “redirect” or “redirected”, as in “redirected from”.

But the reality is that nobody but Facebook actually knows what it stands for. (If you are someone who can prove us wrong, please do! Let us know in a comment what it stands for!)

Note: The Internet Patrol is completely free, and reader-supported. If something that you find here helps you, please consider supporting us. We also earn a small amount from ads and Amazon links:

In the World Wide Web, a query string is the part of a uniform resource locator (URL) containing data that does not fit conveniently into a hierarchical path structure. The query string commonly includes fields added to a base URI by a Web browser or other client application, for example as part of an HTML form.

A web server can handle a Hypertext Transfer Protocol request either by reading a file from its file system based on the URL path or by handling the request using logic that is specific to the type of resource. In the case that special logic is invoked the query string will be available to that logic for use in its processing, along with the path component of the URL.

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OWASP TOP !0

Injection. Injection flaws, such as SQL, NoSQL, OS, and LDAP injection, occur when untrusted data is sent to an interpreter as part of a command or query. The attacker’s hostile data can trick the interpreter into executing unintended commands or accessing data without proper authorization. Broken Authentication. Application functions related to authentication and session management are often implemented incorrectly, allowing attackers to compromise passwords, keys, or session tokens, or to exploit other implementation flaws to assume other users’ identities temporarily or permanently. Sensitive Data Exposure. Many web applications and APIs do not properly protect sensitive data, such as financial, healthcare, and PII. Attackers may steal or modify such weakly protected data to conduct credit card fraud, identity theft, or other crimes. Sensitive data may be compromised without extra protection, such as encryption at rest or in transit, and requires special precautions when exchanged with the browser. XML External Entities (XXE). Many older or poorly configured XML processors evaluate external entity references within XML documents. External entities can be used to disclose internal files using the file URI handler, internal file shares, internal port scanning, remote code execution, and denial of service attacks. Broken Access Control. Restrictions on what authenticated users are allowed to do are often not properly enforced. Attackers can exploit these flaws to access unauthorized functionality and/or data, such as access other users’ accounts, view sensitive files, modify other users’ data, change access rights, etc. Security Misconfiguration. Security misconfiguration is the most commonly seen issue. This is commonly a result of insecure default configurations, incomplete or ad hoc configurations, open cloud storage, misconfigured HTTP headers, and verbose error messages containing sensitive information. Not only must all operating systems, frameworks, libraries, and applications be securely configured, but they must be patched/upgraded in a timely fashion. Cross-Site Scripting XSS. XSS flaws occur whenever an application includes untrusted data in a new web page without proper validation or escaping, or updates an existing web page with user-supplied data using a browser API that can create HTML or JavaScript. XSS allows attackers to execute scripts in the victim’s browser which can hijack user sessions, deface web sites, or redirect the user to malicious sites. Insecure Deserialization. Insecure deserialization often leads to remote code execution. Even if deserialization flaws do not result in remote code execution, they can be used to perform attacks, including replay attacks, injection attacks, and privilege escalation attacks. Using Components with Known Vulnerabilities. Components, such as libraries, frameworks, and other software modules, run with the same privileges as the application. If a vulnerable component is exploited, such an attack can facilitate serious data loss or server takeover. Applications and APIs using components with known vulnerabilities may undermine application defenses and enable various attacks and impacts. Insufficient Logging & Monitoring. Insufficient logging and monitoring, coupled with missing or ineffective integration with incident response, allows attackers to further attack systems, maintain persistence, pivot to more systems, and tamper, extract, or destroy data. Most breach studies show time to detect a breach is over 200 days, typically detected by external parties rather than internal processes or monitoring.