Computer science boffins have demonstrated a side-channel attack technique that bypasses recently-introduced privacy defenses, and makes even the Tor browser subject to tracking. The result: it is possible for malicious JavaScript in one web browser tab to spy on other open tabs, and work out which websites you’re visiting.

This information can be used to target adverts at you based on your interests, or otherwise work out the kind of stuff you’re into and collect it in safe-keeping for future reference.

Researchers Anatoly Shusterman, Lachlan Kang, Yarden Haskal, Yosef Meltser, Prateek Mittal, Yossi Oren, Yuval Yarom – from Ben-Gurion University of the Negev in Israel, the University of Adelaide in Australia, and Princeton University in the US – have devised a processor cache-based website fingerprinting attack that uses JavaScript for gathering data to identify visited websites.

The technique is described in a paper recently distributed through ArXiv called “Robust Website Fingerprinting Through the Cache Occupancy Channel.”

“The attack we demonstrated compromises ‘human secrets’: by finding out which websites a user accesses, it can teach the attacker things like a user’s sexual orientation, religious beliefs, political opinions, health conditions, etc.,” said Yossi Oren (Ben-Gurion University) and Yuval Yarom (University of Adelaide) in an email to The Register this week.

It’s thus not as serious as a remote attack technique that allows the execution of arbitrary code or exposes kernel memory, but Oren and Yarom speculate that there may be ways their browser fingerprinting method could be adapted to compromise computing secrets like encryption keys or vulnerable installed software.

Source: Talk about a cache flow problem: This JavaScript can snoop on other browser tabs to work out what you’re visiting • The Register