An information disclosure vulnerability was found in modern CPUs. By exploiting this vulnerability malicious users can obtain sensitive information. This vulnerability can be exploited remotely via malicious web page through a timing side-channel attack using JavaScript.

Technical details

Vendor has disabled or reduced the precision of several time sources in Firefox. The precision of performance.now() has been reduced from 5μs to 20μs, and the SharedArrayBuffer feature has been disabled because it can be used to construct a high-resolution timer.

Mozilla Firefox earlier than 57.0.4
Mozilla Firefox ESR earlier than 52.6

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Mozilla Foundation Security Advisory 2018-01