True.

It is a bait-and-switch attack that will lead to a malware infection, using a fake adobe download notice, a much more common tactic than one might think.

That the root cause is an infected router (fixable by downloading the latest firmware that fixes security holes and bugs in the prior version), is not to disprove that was or is not the cause. Information was provided above for others who may be following this thread and who may not be aware of this tactic.

They can now check to see if there is indeed a newer version of Adobe Flash, using the link provided above, and can safely ignore the malicious warning if there is no newer version. Never click on something just because it says to do so. Suspicion is how you found the infected router, so…