"We have identified and are working to fix an unlimited memory growth issue affecting DX11 Windows users and all Mac users. Ideally, we should release a build with the fix early next week.
In the meantime, typing /console gxrestart in chat will return the client to normal memory usage (but it will still continue to increase after that). On Windows, using DX12 or DX11 Legacy backends should completely eliminate the error.
For those interested in the code side of things, the error was that the call to std::deque::clear() was incorrectly placed in a block of code that only compiles for internal clients. This led to the fact that the bug never showed up in our internal testing, but led to unlimited memory growth in public clients."
Here is the answer.