What are the risks of GET requests on opt-out links?

6 Marketer opinions 3 Expert opinions 3 Technical articles 2 Resources

Summary

Using GET requests for opt-out links presents numerous risks across security, functionality, and user experience. Experts, marketers, and technical documentation agree that GET requests are inherently insecure, easily exploited by malicious actors for unauthorized unsubscriptions, and vulnerable to CSRF attacks. Furthermore, GET requests violate established web standards regarding idempotency and safety, can be inadvertently triggered by bots, and expose sensitive data. This practice negatively impacts customer experience and overall email program health.

Key findings

Inherent Insecurity: GET requests are easily forged, leading to unauthorized opt-outs.
CSRF Vulnerability: Susceptible to Cross-Site Request Forgery (CSRF) attacks, allowing attackers to trigger unsubscriptions.
Standards Violation: Violates HTTP standards of idempotency and safety, as GET requests should not modify data.
Bot Triggered Actions: Bots and crawlers inadvertently trigger opt-outs, leading to unintended consequences.
Data Exposure: Exposes sensitive data in server logs and browser history, creating security vulnerabilities.
Negative User Experience: Accidental or malicious unsubscriptions negatively impact customer experience.
Abuse Potential: Malicious actors can abuse GET requests to harm legitimate email programs.

Key considerations

Employ POST Requests: Use POST requests for sensitive actions like unsubscriptions to ensure security and prevent unauthorized actions.
Implement CSRF Protection: Implement CSRF tokens to prevent Cross-Site Request Forgery attacks.
Bot Mitigation: Employ techniques to identify and prevent bots from triggering actions.
Secure Logging Practices: Implement secure logging practices to avoid exposing sensitive information.
Double Opt-Out Confirmation: Consider a double opt-out process to confirm unsubscriptions and prevent accidental or malicious removals.
Adhere to HTTP Standards: Ensure adherence to HTTP standards for methods like GET (safety and idempotency).

What email marketers say
6Marketer opinions

Using GET requests for opt-out links poses several risks, primarily due to their inherent insecurity and susceptibility to abuse. These risks include the potential for attackers to forge requests and unsubscribe users without their consent, vulnerability to Cross-Site Request Forgery (CSRF) attacks, accidental unsubscriptions triggered by bots and crawlers, exposure of data in server logs and browser history, and a negative impact on customer experience due to unintended or malicious unsubscriptions.

Key opinions

Insecurity: GET requests are inherently insecure because they can be easily forged by attackers, leading to unintended opt-outs.
CSRF Vulnerability: GET requests can be vulnerable to Cross-Site Request Forgery (CSRF) attacks, where an attacker tricks a user into executing unwanted actions.
Bot Triggered: Bots and search engine crawlers can inadvertently trigger unsubscribe actions.
Data Exposure: GET requests can expose data in server logs and browser history, creating security vulnerabilities.
Negative Customer Experience: Using GET requests can negatively impact customer experience due to accidental or malicious unsubscriptions.

Key considerations

Security Measures: Implement POST requests instead of GET requests for sensitive actions like unsubscriptions to enhance security.
Idempotency: Ensure that unsubscribe actions are not triggered by simple GET requests to maintain the safety and idempotency of HTTP methods.
Bot Mitigation: Consider implementing measures to prevent bots and crawlers from inadvertently triggering unsubscribe actions.
Logging Practices: Review logging practices to avoid exposing sensitive data related to unsubscribe actions in server logs.
User Experience: Prioritize a positive customer experience by minimizing the risk of accidental or malicious unsubscriptions.

Marketer view

Email marketer from Webmaster Forum warns about bots and search engine crawlers inadvertently triggering unsubscribe actions if GET requests are used for opt-out links.

May 2023 - Webmaster Forum

Marketer view

Email marketer from Reddit shares concerns about accidental unsubscriptions due to bots or crawlers following GET-based unsubscribe links.

January 2024 - Reddit

Marketer view

Email marketer from Marketing Land stresses that using GET requests for unsubscribe links can negatively impact customer experience due to potential for accidental or malicious unsubscriptions.

March 2022 - Marketing Land

Marketer view

Email marketer from Security Blog warns that GET requests for actions like unsubscribing expose users to one-click attacks and CSRF vulnerabilities.

January 2025 - Security Blog

Marketer view

Email marketer from Stack Overflow explains that GET requests are inherently insecure because they can be easily forged by attackers, leading to unintended opt-outs.

July 2021 - Stack Overflow

Marketer view

Email marketer from OWASP explains that GET requests can be vulnerable to Cross-Site Request Forgery (CSRF) attacks, where an attacker tricks a user into executing unwanted actions on a web application in which they're authenticated.

July 2021 - OWASP

What the experts say
3Expert opinions

Using GET requests for opt-out links carries significant risks. Experts warn about the potential for abuse by malicious actors who can unsubscribe users without consent, and the likelihood of bots and crawlers inadvertently triggering unsubscribe actions. The consensus is that relying on GET requests for such sensitive operations can lead to serious problems.

Key opinions

Abuse Potential: Malicious actors can exploit GET requests to unsubscribe users without their consent.
Bot Interference: Bots and crawlers can inadvertently trigger unsubscribe actions.
Serious Consequences: Using GET requests for opt-outs can create major problems and should be avoided.

Key considerations

Security: Implement secure methods, like POST requests, to prevent unauthorized unsubscriptions.
Bot Mitigation: Take steps to prevent bots from triggering unsubscribe actions.
Alternative Methods: Explore alternative, more secure, methods for handling opt-out requests.

Expert view

Expert from Word to the Wise explains that bots and crawlers can inadvertently trigger unsubscribe actions if GET requests are used for opt-out links, leading to unintended consequences for subscribers.

November 2021 - Word to the Wise

Expert view

Expert from Spam Resource explains that using GET requests for unsubscribe links can be abused by malicious actors, potentially unsubscribing users without their consent and harming legitimate email programs.

April 2021 - Spam Resource

Expert view

Expert from Email Geeks states if a GET request to your opt-out link causes any action to happen you’re already in a world of pain.

July 2024 - Email Geeks

What the documentation says
3Technical articles

Using GET requests for opt-out links violates established web standards. Documentation highlights that GET requests should be idempotent and safe, meaning they should not modify data or cause side effects. Furthermore, employing GET for sensitive operations like unsubscribing can expose data in server logs and browser history, creating security vulnerabilities.

Key findings

Violates Idempotency: GET requests should be idempotent, but using them for opt-outs modifies data, violating this principle.
Violates Safety: GET requests should be safe and not cause side effects; unsubscribing users violates this.
Data Exposure: GET requests for sensitive operations can expose data in server logs and browser history.

Key considerations

Use POST Instead: Employ POST requests for actions that modify data, such as unsubscribing, to adhere to web standards.
Security Best Practices: Avoid using GET for sensitive operations to mitigate the risk of data exposure.
Adherence to Standards: Ensure that web applications adhere to established HTTP method guidelines (idempotency and safety).

Technical article

Documentation from MDN Web Docs explains that GET requests should be idempotent, meaning multiple identical requests should have the same effect as a single request. Using GET for opt-outs violates this principle as it modifies data.

September 2021 - MDN Web Docs

Technical article

Documentation from IETF's RFC 2616 states the GET method should be safe, meaning it should not cause any side effects. Using GET to unsubscribe users violates this principle.

June 2021 - RFC 2616

Technical article

Documentation from SANS Institute explains that GET requests, especially when used for sensitive operations, can expose data in server logs and browser history, creating potential security vulnerabilities.

April 2024 - SANS Institute

California Consumer Privacy Act (CCPA) | State of California ...

Updated on March 13, 2024 The California Consumer Privacy Act of 2018 (CCPA) gives consumers more control over the personal information that businesses collect about them and the CCPA regulations provide guidance on how to implement the law.

State of California - Department of Justice - Office of the Attorney General