Client is Getting "Threat found" Error (JS/Packed.Agent.Q) When Logging into EE Control Panel. I can't replicate here.

My client is getting a “Threat found” error (JS/Packed.Agent.Q) when logging into their EE control panel and/or editing entries. They’ve used Firefox and Chrome. Both on their office network. I can’t replicate here in any of my browsers.

The site is on EE 5.4.3.

Any ideas how to troubleshoot?

Thank you for your help.