I’m running into an issue with Internet Explorer’s security features and need some help.
I built a web application where users can download HTML files. These files have a form with some hidden input fields that gets automatically submitted using JavaScript when opened. This lets users save their edited data from the website to their computer.
The problem is that some users see a yellow security warning bar in IE when they try to open the downloaded file. IE thinks the HTML is trying to run ActiveX controls, but it’s just basic JavaScript calling the form’s submit() method.
What’s weird is that if someone emails the exact same HTML file and the recipient saves it and opens it, no warning appears. It seems like IE treats files downloaded from websites differently than files received through email.
Does anyone know where I can find official documentation about this IE security behavior? Also, is there a way to prevent this warning from showing up for legitimate JavaScript code?
Thanks for any help!
This is actually how Internet Explorer’s security model works. When you download an HTML file from a website, IE adds an “Alternate Data Stream” (ADS) that marks the file as coming from the Internet zone. This triggers the security warning because IE applies stricter policies to files from untrusted sources. Emailed files don’t trigger this warning because email clients typically don’t preserve these zone markers when saving attachments. You can check this yourself - right-click your downloaded HTML file, hit Properties, and look for an “Unblock” button at the bottom. That’s the zone marker doing its thing. There’s no reliable way to suppress this warning from your web app since it’s a client-side security feature. The warning shows up for any downloaded HTML with JavaScript, no matter how harmless the code is. Microsoft built this specifically to protect users from malicious downloads. One workaround some developers use: generate the data as a different file format that doesn’t trigger warnings, then tell users to rename the extension if they need to.
yeah, i’ve hit this too. the zone identifier fix works, but here’s what else you can try: serve the file with different mime types or use data urls instead of file downloads. some devs wrap their js to avoid ie’s activex detection, but it’s finicky and depends on your specific code.
You’re hitting the Mark of the Web (MOTW) issue. IE automatically tags downloaded files with this security identifier, forcing them into the restricted Internet zone. Microsoft’s docs on this are scattered across different KB articles and MSDN pages - it’s a pain to find the exact info you need. I found out the hard way that the warning threshold is super sensitive. Even basic DOM stuff can trigger it. What worked for me was restructuring the JavaScript to avoid running immediately on page load. Instead of auto-submitting the form, I added a button click or some other user action. This cut down the security warnings big time because IE cares way less about user-initiated JavaScript than automatic execution. You’re right about the email difference too - most email clients strip the zone info when saving attachments, so those files open clean.