Summary
Email security filters are increasingly sophisticated, with some systems now capable of executing JavaScript embedded within email landing pages. This capability, while designed to detect and prevent phishing or malware, can inadvertently lead to artificial clicks and confirmations, particularly for double opt-in processes. When an opt-in email contains a link to a page with JavaScript that automatically submits a form (e.g., to confirm a subscription), security filters scanning the link might trigger this JavaScript, thereby auto-confirming the subscription without actual user interaction. This can skew engagement metrics and potentially add unverified subscribers to your list.
Key findings
- Filter sophistication: Modern email security filters, particularly those from providers like Microsoft, are designed to not just render HTML, but also execute JavaScript on linked pages to thoroughly scan for malicious content and phishing attempts.
- Unintended confirmation: If a landing page for an email's link includes JavaScript that auto-submits a form (such as for double opt-in confirmation), security filters visiting the link may inadvertently trigger this submission, leading to an unwanted confirmation.
- Impact on metrics: Automated clicks and confirmations by filters can significantly skew email engagement metrics, making it difficult to gauge genuine subscriber interest and activity.
- Security measure: This behavior, while problematic for marketers, is an essential part of the arms race against scammers who use JavaScript to obfuscate malicious content or create dynamic phishing forms.
Key considerations
- JavaScript impact: Review any JavaScript on your landing pages that links to your emails, especially those for opt-in confirmations. Auto-submitting forms are a prime candidate for this unintended behavior.
- Manual interaction: To ensure genuine user intent, rely on explicit user actions, like a manual button click, for critical steps such as subscription confirmation. This adheres to the standard web idiom for intentional user behavior.
- Alternative confirmation methods: Consider implementing alternative methods for confirmation that filters cannot easily mimic, such as requiring users to copy-paste a unique six-digit code into a form. This can help prevent false positives from automated systems.
- Monitoring: Monitor your logs for suspicious IPs, especially those from major email providers like Microsoft, to identify if security filters are still triggering unintended actions on your landing pages. MailSoar.com's blog on email click bots provides further insight.
What email marketers say
Email marketers often face a dilemma between optimizing user experience and ensuring accurate data collection. The discovery that email security filters are executing JavaScript on landing pages and causing unintended actions, such as auto-confirming opt-ins, highlights a new challenge in this balancing act. Marketers prioritize a smooth subscriber journey but are increasingly forced to re-evaluate their technical implementations to prevent skewed metrics and maintain data integrity, even if it means adding an extra step for the user.
Key opinions
- Usability versus accuracy: The desire to remove unnecessary steps for subscribers (like an extra click for confirmation) often leads to implementing solutions like JavaScript auto-submits, but this can backfire due to filter behavior.
- New headache: While marketers are accustomed to filters following links, the execution of JavaScript and the subsequent auto-confirmation of actions like opt-ins is a surprising and frustrating development that complicates email list management.
- Accepting added friction: Some marketers are resigned to adding an extra step for users (e.g., a manual click) to ensure genuine engagement, viewing it as a necessary evil in the face of evolving security measures, similar to 2FA.
Key considerations
- Re-evaluating user flows: Marketers should reconsider any user flows that rely on JavaScript for critical actions like opt-in confirmation, to avoid unintended filter-driven interactions.
- Data integrity: The potential for skewed metrics means marketers need to be vigilant in identifying and filtering out bot-driven engagement from their analytics.
- Subscriber experience: While striving for minimal friction, marketers must weigh the benefits of a one-click process against the risks of illegitimate confirmations and the potential damage to list quality.
- Adaptation: The evolving landscape of email security requires marketers to continually adapt their strategies and technologies to ensure reliable data and good sender reputation. Interspire.com discusses automated email clicks and how to respond.
Marketer view
Email marketer from Email Geeks notes that they recently discovered opt-in emails sent to Microsoft systems are being auto-clicked. They observed that Microsoft's filters visit the confirmation link, run the JavaScript, and automatically confirm the subscription without user interaction, which is a significant challenge for their double opt-in process.
Marketer view
Email marketer from Email Geeks states that while they have long experienced filters following links, the filters executing JavaScript to auto-submit forms is a new and unexpected behavior. They acknowledge the importance of headless rendering for phishing detection but regret the added friction for subscribers.
What the experts say
Experts in email deliverability and security confirm that security filters regularly follow links to inspect content for threats. The execution of JavaScript is a logical evolution of this process, allowing filters to uncover hidden or dynamically generated malicious elements. While this behavior is a legitimate defense mechanism, it creates unforeseen side effects for senders, especially those relying on JavaScript for critical user actions like opt-in confirmations. The consensus among experts is that this is an unavoidable part of the 'arms race' between malicious senders and security providers.
Key opinions
- Expected behavior: Security filters following links to check for malicious content is not a new phenomenon, and is an expected part of email security protocols.
- JavaScript as a detection tool: Running JavaScript is crucial for filters to detect sophisticated phishing attempts where malicious content is hidden or dynamically loaded via scripts.
- Data separation: Distinguishing between a user-initiated click and a script-initiated POST request (even if the script is triggered by a filter) can provide more granular data for analysis.
- Arms race: The evolution of filter behavior, including JavaScript execution, is a direct response to the ongoing 'arms race' between blackhat and whitehat actors in the email security landscape.
Key considerations
- Traditional submission: Opting for a classic HTML form submit button, rather than JavaScript-driven auto-submission, can mitigate the risk of filters triggering unintended actions. This is often the more robust approach for ensuring user intent.
- Distinguishing actions: Implementing separate endpoints for JavaScript-triggered actions versus explicit button clicks can help differentiate between automated visits and genuine user engagement, providing more accurate tracking.
- Delayed execution: While not foolproof, introducing a slight delay (e.g., 3-4 seconds) before JavaScript execution might allow security scanners to complete their analysis without triggering the action, although sophisticated scanners may still bypass this.
- Accepting the trade-off: Marketers may need to accept a slight increase in user friction to gain more reliable data and ensure the integrity of their opt-in processes. Spiceworks Community provides insight into how email security products scan links.
Expert view
Deliverability expert from Email Geeks explains that security filters have long been following links and checking for malicious content, and this often affects metrics like open rates and one-click unsubscribes. They suggest that JavaScript is likely the cause of the auto-confirmation issue.
Expert view
Deliverability expert from Email Geeks recommends using an old-fashioned submit element for forms, as this is more likely to resolve the issue of filters inadvertently triggering form submissions compared to relying on JavaScript.
What the documentation says
Official documentation and security research papers confirm that advanced email security systems employ dynamic analysis techniques, including headless browser rendering, to fully evaluate the potential risks of embedded links. This involves executing JavaScript to detect polymorphic malware, phishing kits, and other evasive threats that might not be visible in static HTML. The primary goal is to protect end-users, even if it occasionally results in unintended side effects like auto-clicking or auto-confirming actions on linked pages.
Key findings
- Dynamic analysis: Security filters utilize dynamic analysis, often involving virtualized environments or headless browsers, to simulate a user's interaction with a linked page, including the execution of JavaScript.
- Threat detection: The execution of JavaScript is a critical component for detecting advanced threats like drive-by downloads, credential harvesting, and content cloaking used in phishing campaigns.
- User protection: The overriding objective of these security mechanisms is to safeguard the recipient, which sometimes leads to actions that might appear as unwanted automated interactions from the sender's perspective.
- URL rewriting: Many email security systems rewrite URLs within emails to route them through their scanning infrastructure, ensuring that any click is first vetted. This process often involves rendering the page.
Key considerations
- Adherence to standards: Design landing pages to strictly adhere to web standards for user interaction, ensuring that critical actions are explicitly triggered by user input (like a button click) rather than automated JavaScript.
- Reduced reliance on JS for actions: Minimize the use of JavaScript for immediate, critical actions upon page load, especially for sensitive processes like opt-in confirmations, to prevent unintended activation by security scanners.
- Understanding filter behavior: Familiarize yourself with documentation from major mailbox providers or security vendors regarding their scanning processes and how they handle dynamic content to better anticipate filter behavior. TechTarget.com provides a comprehensive definition of how spam filters work.
- Auditing links: Regularly audit your email links and their corresponding landing pages to ensure that no JavaScript is inadvertently creating vulnerabilities for unintended filter interactions. This is a key aspect of maintaining link integrity.
Technical article
Documentation from Interspire.com states that email security robots are designed to automatically click on links within emails to scan for potential security threats. These bots look for malware or phishing attempts by interacting with the content.
Technical article
MailSoar.com's documentation explains that email spammer bots are automated software programs intended to imitate real users. These programs click on links in emails, which can significantly skew analytics and impact the perceived effectiveness of email campaigns.
Related resources
5 resources
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