User Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/536.5 (KHTML, like Gecko) Chrome/19.0.1084.1 Safari/536.5 Steps to reproduce: Steps: - Install BrandMyMail 0.19.6 addon from repository https://addons.mozilla.org/en-US/firefox/addon/brandmymail/ - Activate it through its site - In new tab open gmail.com and login with related account - Click compose new message - Click Preview button - Close the Gmail tab and check about:memory Actual results: There is a zombie compartment ├───30.14 MB (16.69%) -- compartment(https://mail.google.com/mail/u/0/?shva=1) │ │ ├──13.95 MB (07.73%) -- gc-heap │ │ │ ├───3.74 MB (02.07%) -- arena │ │ │ │ ├──3.47 MB (01.92%) ── unused │ │ │ │ └──0.27 MB (00.15%) ++ (2 tiny) │ │ │ ├───3.73 MB (02.07%) -- objects │ │ │ │ ├──1.87 MB (01.04%) ── non-function │ │ │ │ └──1.86 MB (01.03%) ── function │ │ │ ├───3.15 MB (01.75%) ── scripts │ │ │ ├───2.70 MB (01.49%) ++ shapes │ │ │ └───0.63 MB (00.35%) ++ (2 tiny) │ │ ├───4.34 MB (02.40%) ── script-data │ │ ├───3.77 MB (02.09%) ── analysis-temporary │ │ ├───3.46 MB (01.92%) -- type-inference │ │ │ ├──2.89 MB (01.60%) ── script-main │ │ │ └──0.57 MB (00.32%) ++ (2 tiny) │ │ ├───2.58 MB (01.43%) ++ (3 tiny) │ │ └───2.03 MB (01.12%) ++ shapes-extra Expected results: No zombies

Thanks for the report, Andrii! We already have a bug on file for BrandMyMail, so I'll mark this as a duplicate.