If it's an inside job, it's very bad. Basically everything could be compromised.
Shouldn't the commits be multi-keyed?
edit: multisig
I don't know how ledger runs their business, but I got a screenshot of a tweet from another chat (twitter user @MatthewLilley) which says
  1. They are loading JS from a CDN
  2. They are not version locking loaded JS
  3. They had their CDN compromised
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