It has been great until recently, when I started experiencing severe lagging in Firefox and discovered that this extension is a memory hog.

Here's my `top` with HTTPS Everywhere enabled:

PID PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
9036 20 0 14.6g 218564 107332 S 0.0 1.3 0:25.73 WebExtensions

...and when the add-on is disabled:

PID PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
9036 20 0 8970992 199000 107204 S 0.3 1.2 0:26.00 WebExtensions

I have no idea why it needs to commit 14Gb of virtual memory, but that does not sound reasonable at all. I'll keep it switched off for now to see if the overall performance improves.

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 20.04.2 LTS
Release: 20.04
Codename: focal

$ uname -a
Linux xxxxx 5.4.0-66-generic #74-Ubuntu SMP Wed Jan 27 22:54:38 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

$ firefox --version
Mozilla Firefox 86.0

HTTPS Everywhere Version 2021.1.27