User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Firefox/68.0

Steps to reproduce:

I tested this in both Dev 77.0b2 and Nightly 78.0a1, both 64-bit, on Windows 10.

1. Launch Firefox with new profile
2. Enable containers in about:config
3. Open a container tab
4. Load yahoo.com, close tab
5. Delete container

Actual results:

Options / Privacy & Security / Manage Data reports that yahoo.com is still storing 1 cookie and 64 KB of data

This happens inconsistently, about every 6-7 times. Cnn.com and youtube.com have also left data behind, up to 10 cookies in one instance.

Expected results:

All cookies & site data should be deleted from a removed container.

Because this bug's Severity is normal and has not been changed, and this bug's priority is -- (none,) indicating it has has not been previously triaged, the bug's Severity is being updated to -- (default, untriaged.)

The severity field is not set for this bug.
:johannh, could you have a look please?

For more information, please visit auto_nag documentation.

I think this is a dupe of bug 1633697