Google has demonstrated exploiting the Spectre CPU attack remotely over the web:

Today, we’re sharing proof-of-concept (PoC) code that confirms the practicality of Spectre exploits against JavaScript engines. We use Google Chrome to demonstrate our attack, but these issues are not specific to Chrome, and we expect that other modern browsers are similarly vulnerable to this exploitation vector. We have developed an interactive demonstration of the attack available at ; the code and a more detailed writeup are published on Github here.

The demonstration website can leak data at a speed of 1kB/s when running on Chrome 88 on an Intel Skylake CPU. Note that the code will likely require minor modifications to apply to other CPUs or browser versions; however, in our tests the attack was successful on several other processors, including the Apple M1 ARM CPU, without any major changes.