I have the same issue as @TaLoche with 1.4.2 after upgrading from 1.4.1.

What sort of effort would it take to log users being added or removed from groups, along with the user that added/removed them?

@baris
This worked perfectly. Thank you!

1.4.1 NodeBB install, going to /posts/flags or Manage -> Flags in the ACP crashes NodeBB with the following error in the log. Any ideas?

22/12 03:38:59 [8795] - error: TypeError: Cannot read property 'cid' of undefined
    at /opt/nodebb/src/posts/summary.js:68:51
    at Array.forEach (native)
    at async.waterfall.plugins.fireHook.posts (/opt/nodebb/src/posts/summary.js:61:11)
    at fn (/opt/nodebb/node_modules/async/lib/async.js:746:34)
    at /opt/nodebb/node_modules/async/lib/async.js:1213:16
    at /opt/nodebb/node_modules/async/lib/async.js:166:37
    at /opt/nodebb/node_modules/async/lib/async.js:706:43
    at /opt/nodebb/node_modules/async/lib/async.js:167:37
    at /opt/nodebb/node_modules/async/lib/async.js:1209:30
    at /opt/nodebb/node_modules/async/lib/async.js:726:13
    at /opt/nodebb/node_modules/async/lib/async.js:52:16
    at done (/opt/nodebb/node_modules/async/lib/async.js:246:17)
    at /opt/nodebb/node_modules/async/lib/async.js:44:16
    at /opt/nodebb/node_modules/async/lib/async.js:723:17
    at /opt/nodebb/node_modules/async/lib/async.js:167:37
    at /opt/nodebb/src/posts/summary.js:132:5
TypeError: Cannot read property 'cid' of undefined
    at /opt/nodebb/src/posts/summary.js:68:51
    at Array.forEach (native)
    at async.waterfall.plugins.fireHook.posts (/opt/nodebb/src/posts/summary.js:61:11)
    at fn (/opt/nodebb/node_modules/async/lib/async.js:746:34)
    at /opt/nodebb/node_modules/async/lib/async.js:1213:16
    at /opt/nodebb/node_modules/async/lib/async.js:166:37
    at /opt/nodebb/node_modules/async/lib/async.js:706:43
    at /opt/nodebb/node_modules/async/lib/async.js:167:37
    at /opt/nodebb/node_modules/async/lib/async.js:1209:30
    at /opt/nodebb/node_modules/async/lib/async.js:726:13
    at /opt/nodebb/node_modules/async/lib/async.js:52:16
    at done (/opt/nodebb/node_modules/async/lib/async.js:246:17)
    at /opt/nodebb/node_modules/async/lib/async.js:44:16
    at /opt/nodebb/node_modules/async/lib/async.js:723:17
    at /opt/nodebb/node_modules/async/lib/async.js:167:37
    at /opt/nodebb/src/posts/summary.js:132:5
22/12 03:38:59 [8795] - info: [app] Shutdown (SIGTERM/SIGINT) Initialised.
22/12 03:38:59 [8795] - info: [app] Database connection closed.
22/12 03:38:59 [8795] - info: [app] Web server closed to connections.
22/12 03:38:59 [8795] - info: [app] Shutdown complete.
[cluster] Child Process (8795) has exited (code: 1, signal: null)
[cluster] Spinning up another process...