🤖Introduction

In June 2025, privacy researchers dropped a bombshell report revealing that Meta and Yandex secretly circumvented Android’s privacy protections to track users' web activity, even in incognito mode. Using an obscure method that bypassed traditional sandboxing barriers, both companies linked anonymous browser data to user accounts in their apps, undermining years of privacy advancements.

👾The Exploit:

😵‍💫What Is "Local Mess"?

Researchers from Radboud University, KU Leuven, and IMDEA uncovered a previously unknown technique now dubbed "Local Mess." This exploit allowed native apps like Facebook, Instagram, and Yandex to intercept browsing identifiers generated by their tracking scripts (like Meta Pixel or Yandex Metrica) in mobile browsers.

These scripts sent tracking IDs to the device's localhost interface via methods like TCP or WebRTC (STUN). From there, the installed apps listened on the same port, capturing the data. This process effectively de-anonymised users by tying their incognito or cookie-less browsing to their logged-in app identities.

🤔Why It Matters:

This discovery exposes a major privacy gap. Users operating in incognito mode or with cookie blockers believed their actions were anonymised. But this exploit made such protections meaningless for Android users with affected apps installed.

Even more troubling: Meta began using this technique around September 2024, while Yandex had been using a similar method since 2017. This indicates a long-standing, largely undetected violation of Android’s app sandboxing model.

🐘The Scale of the Problem

• Meta Pixel appears on roughly 5.8 million websites worldwide.
• Yandex Metrica is embedded in over 3 million sites.
• Researchers found the tracking happening on at least 16,000 websites in the EU alone for Meta and 1,300 for Yandex.

With such widespread web tracker distribution, millions of Android users may have unknowingly had their browsing habits linked to their personal app data.

🫠Reactions from Tech Companies

• Google: Confirmed that this behaviour violated Play Store policies. Chrome updates are being deployed to mitigate the loophole.
• Meta has paused the use of this technique and is reportedly in discussions with Google.
• Yandex: Claims it never collected sensitive data and has committed to discontinuing this method.
• Browsers: Brave, DuckDuckGo, and Firefox have issued or announced updates to block such local loopback exploits.

🏋️How You Can Protect Yourself

Until permanent fixes are rolled out, here are some steps you can take:

• Uninstall apps like Facebook, Instagram, or Yandex if privacy is a priority.
• Use privacy-first browsers like DuckDuckGo, Brave, or Firefox instead of Chrome.
• Avoid apps when possible use mobile websites for occasional tasks.

Clear app permissions and disable background activity for unused apps.

💡Conclusion

This incident underscores how tech giants can still find novel ways to invade user privacy even in supposedly protected environments. As privacy evolves into an arms race, users must stay informed and proactive. While companies like Google and browser developers race to close this loophole, it’s clear that trust in mobile platforms and their security models needs serious reevaluation.