Just this week I started having problems where Thunderbird hangs, apparently due to a memory leak, after viewing S/MIME signed emails containng embedded hyperlinks to a secure site that requires my certificate to login. This is on a Dell Precision 7550 running Windows 10, and Thunderbird 91.9.0 (also the previous installed version - I believe it was 91.8.1). After clicking on such an email (which come from a known address and are forwarded to a specific folder by a rule), the email is slow or fails to load into the display window. Subsequent clicking on other folders has a delayed response or never responds. I sometimes get a message at the top saying (Not Responding), sometimes I can click on other email records or switch folders, but emails no longer display contents in the viewing pane - it stays blank. The other think I noticed is the blue bar at the lower right which appears when compacting shows up with the bar at 100% but never goes away. To end the task I must use Task Manager. This behavior only occurs after I have clicked on signed email with links (but not the link itself) that require a login using the smartcard certificates. Prior to looking at the signed email with these links, TB operates normally (aside from the endemic new user interface issues) when viewing other signed or unsigned emails. Curiously, in my most recent restart of the program, I clicked on several messages from the source of the emails with the hyperlinks, but ones that did not link to the secure files requiring certificate access. One of these was encrypted and opened normally with my certificate, and after accessing this email, the emails with the secure hyperlink opened normally and did not result in TB not responding. I believe this has something to do with TB and S/MIME configuration, and have verified this behavior does not occur in Troubleshooting mode. However, in Troubleshooting mode, I cannot access my PKI S/MIME certificates as the Broadcom smart card device is not present. I am attaching a task manager snip showing the memory leak (the memory used continues to increase with time, the CPU percentage stays roughly the same - unfortunately this file upload has a perpetually spinning circle and still says it is uploading, so I may have to try again). I have also included the Device Manager view associated with the S/MIME certificates in regular and troubleshooting mode which show the internal Broadcom device is not present in the latter instance. I need to have the functionality and security provided by the smartcard S/MIME certificates, so this is a major problem for me.