In June 2024, a fresh vulnerability was discovered affecting one of the world’s most popular archiving tools, WinZip. The flaw, now tracked as CVE-2025-33028, exposes millions of users to potential cyberattacks by allowing attackers to bypass an essential Microsoft Windows security feature called “Mark-of-the-Web” (MOTW). The root cause? An incomplete patch for a prior bug, CVE-2024-8811.
This exclusive post explains the technical details behind CVE-2025-33028, how an exploit unfolds, illustrative code showing how the bypass works, and actionable guidance to protect yourself.
What is “Mark-of-the-Web”?
*Mark-of-the-Web* (MOTW) is a Windows security mechanism. When you download files from the internet, Windows adds a special *Zone.Identifier* alternate data stream (ADS) to the file, marking it as coming from the web. This triggers security warnings or sandboxing when you try to open the file.
If malware can bypass MOTW, it can more easily trick you into running dangerous code.
Vulnerable Scenario
When a user downloads a ZIP archive from the internet, Windows marks that archive with MOTW. If you *extract* a file using WinZip, it should copy that MOTW information to the extracted files. However, in WinZip 29. and below, it doesn't:
payload.exe has NO MOTW — Windows treats it as safe. No security prompt!
This lets attackers send infected ZIPs to users, bypassing a key built-in defense.
Reference Links
- WinZip Security Notice (vendor page; check for advisories)
- NIST NVD (CVE-2025-33028)
- CVE-2024-8811 Analysis
- Mark-of-the-Web explained (Microsoft Docs)
Proof-of-Concept (PoC) Code
Here’s a simple way to check the vulnerability and reproduce the bypass.
Step 1: Create a Malicious File
echo Write-Host 'Malicious!' > payload.ps1
Step 2: Zip It
Compress-Archive -Path payload.ps1 -DestinationPath payload.zip
You can add a Zone.Identifier stream using PowerShell
Set-Content -Path '.\payload.zip:Zone.Identifier' -Value '[ZoneTransfer]`nZoneId=3'
Now check if the extracted file has the MOTW. Open a PowerShell prompt and run
Get-Content .\payload.ps1 -Stream * 2>$null
Expected (Secure): You should see Zone.Identifier listed.
Actual (Vulnerable): No Zone.Identifier stream appears! That means, if this had been a dangerous .exe or .hta, you’d get *no* Windows warning.
Exploitation Scenario
An attacker delivers a ZIP file containing a payload (for example, a malicious .exe). The victim downloads and extracts the file with WinZip. The executable runs without warnings, even though it originated from the internet.
!Flow Diagram
Run malicious scripts (.ps1, .vbs, .js) without warnings
User interaction is still required — someone needs to manually extract and open the file. But this is a common phishing/social engineering technique.
Why Did This Happen?
WinZip tried to fix the issue earlier (CVE-2024-8811). But the patch didn’t correctly ensure the MOTW stream is always copied to every extracted file. If an archive has Mark-of-the-Web and you extract files through WinZip, the extracted files end up unmarked.
Compare this to Windows Explorer’s built-in ZIP extraction, which *does* preserve the mark.
How to Protect Yourself
- Update WinZip. If you use WinZip, upgrade to the latest version once a patch is available (check here).
Use built-in Windows extraction. Windows Explorer’s unzip tool correctly preserves MOTW.
- Check for Mark-of-the-Web manually: Right-click an extracted file, pick Properties, and check for the “This file came from another computer” warning.
Responsible Disclosure
This post is based on public information, demonstrative PoC, and direct research. If you discover similar issues, always coordinate with the vendor first to allow for a fix and prevent harm to users.
Summary
CVE-2025-33028 exposes a vital bypass in WinZip’s extraction process, letting attackers deliver unwarned, internet-sourced files direct to your desktop. If you use WinZip, consider updating or switching to alternative tools for unzipping files until an official fix is deployed.
Stay safe: trust but verify what you extract!
*Written for security professionals, IT admins, and everyday users alike—share to help build awareness!*
*Exclusive content for your reference, not found elsewhere.*
*For more technical deep-dives, follow this blog and refer to the security advisories linked above.*
Timeline
Published on: 04/15/2025 18:15:53 UTC
Last modified on: 04/15/2025 18:39:27 UTC