Downloaded installer corruptedI

The error message above isn't actually the one you would get from the MacOS "where do you want to install files from" security setting, but it looks a lot like it, so I get the confusion.  That isn't the issue, and it makes sense that those steps didn't help.

What the error message is saying is that the file that's getting stored on your machine is corrupt.  We serve about ~2.5 billion installs/month off a world-class, globally distributed content distribution network.

I'm pretty confident that when the bits leave the source and hit the wire that they're right, because complaints from even 1% of that number would hopelessly overwhelm our ability to respond, and this is the only active complaint I'm aware of.

We send the bits to you over a connection with TLS (transport layer security) enabled, which guarantees with a high degree of certainty that those bits are authentic and unmodified at arrival.  Unless a nation-state has decided to mess with you specifically, you're in pretty good shape on that front.

If we rule out the source and transmission with a reasonable degree of confidence, then we have to look at what happens to those bits once they arrive at the destination (i.e. your machine).

The bits get stored to the local disk, but in this instance, the operating system attempts to open them (a .dmg file is basically a fancy compressed package, like a .zip file), but calculates a hash of the bits in the file, and compares it with the hash that was stored in the header of the file when it was created, and it sees that they don't match.  It then throws the message that you're seeing, which is effectively, "the bits in the file you have don't match the bits that should be there".

Following that logic, here are the things that come to mind:

1. Your disk is full, and the file gets truncated at the point at which you completely run out of space.  Since only part of the file gets stored, it's never going to match the original. 
   
   To confirm, look in Finder > Go > Computer > Macintosh HD (or whatever you named it)
   Choose File > Get Info, and then look at Free Space.  If you don't have > 100MB of disk space free, you're running pretty low, and might have better success if you freed some space up.
   
   
2. The filesystem is corrupted.  The filesystem is basically a little database on the physical disk that keeps track of where individual files start and end.  It does get messed up from time to time, and this could cause things to be written or read inconsistently.  Keep reading.
3. The disk has a physical problem.  There are one or more areas on the disk that are physically damaged, and this file is getting repeatedly written/read from the affected location, or the actual read/write heads are damaged (they come unglued sometimes, etc).
   
   

If you've confirmed that you have free space, then you probably want to rule out problems 2 and 3 next.  The problem is, they're hard to differentiate, and if you have a physical problem that's blossoming from "being a little flaky" into "catastrophic failure", you probably want to grab any important data off the disk before you give it a good workout.  If you don't already have those irreplaceable pictures and secret documents backed up, definitely do that now.  Disk recovery services are crazy expensive.

Once your backups are in order, MacOS provides a nice utility for making sure the disk is in a consistent state.

See the "Try Disk Utility" section:

https://support.apple.com/en-us/HT203176

While you're there, choose Repair Filesystem Permissions (Verify will frequently return clean, but then Repair will still fix a bunch of problems).

Once you've identified and corrected any problems, drag all of the copies of the Flash Player installer (the DMG files) into the trash, empty it, and reboot the machine for good measure.

At that point, download a new copy of the installer from here:

https://get.adobe.com/flashplayer/

If the install still throws a corrupted file error, please let us know, but I think that will get you unstuck.

So I tried downloading with Opera (only other browser I have on my computer) and same result.  I believe this narrows it to an issue with either the way the installer is downloading, or the way my computer is reading the installer.  I was able to install previously by downloading the DMG file to Dropbox first then open Dropbox folder and install from the DMG downloaded to Dropbox.  So I wonder if it's somehow a network issue.

Is there any way I can download the DMG from an Adobe page that doesn't require flash to view? 

Still having the issue.

Hello m_vargas

So this time I just copied and pasted the path directly from your instructions and this is what came back:

... codesign -vvd /Volumes/Adobe\ Flash\ Player\ Installer/Install\ Adobe\ Flash\ Player.app

Executable=/Volumes/Adobe Flash Player Installer/Install Adobe Flash Player.app/Contents/MacOS/Install Adobe Flash Player

Identifier=com.adobe.InstallAdobeFlashPlayer

Format=bundle with Mach-O thin (i386)

CodeDirectory v=20200 size=4737 flags=0x0(none) hashes=229+3 location=embedded

Signature size=8524

Authority=Developer ID Application: Adobe Systems, Inc.

Authority=Developer ID Certification Authority

Authority=Apple Root CA

Timestamp=Dec 2, 2016, 3:40:13 AM

Info.plist entries=22

TeamIdentifier=JQ525L2MZD

Sealed Resources version=2 rules=12 files=80

Internal requirements count=1 size=196

OOOOHHHHH, wait a minute, do you mean the already installed Flash Player app?  Not the one I'm having trouble installing?    Just occurred to me that might be what you're talking about.  You didn't specifically say that and since context was about the installer I thought it was the app in that installer.

Sorry m_vargas I guess I don't know what it means to mount the DMG.  I assumed it meant double click the dmg which is what I did then got info on the app and copy pasted the location.  I can't double click "Install Adobe Flash Player.app" because it gives me the attached error.  Was the source of the original problem.  So I can only assume I'm not understanding the steps because I don't know what I'm doing.  Will stab around and re-read your directions another half dozen times in the hopes I can intuit what you mean.  I do appreciate the help I just have absolutely no clue what I'm doing here.  Problems are so rare on my Mac that I've got very little knowledge of how things work.

Colin Holgate thanks for your reply.  I gave your suggestion a try.  I receive the same error as above.

There is a recent issue that shouldn't be showing on your system, but maybe the same solution will work:

Open the DMG.

Right-Click on Install Adobe Flash Player and choose Show Contents.

Open the folder Contents, then MacOS.

Double-click on the file Adobe Flash Player Install Manager.

In later systems those steps are a way around the apparent installer corruption. It may not be what will fix it for you, but may as well try.

Thanks for the reply.  Tried that link and same result.  Attached screenshot of error.

Any ideas on what's causing this?

I tried the current one, and the DMG mounted ok. It's the one here:

Adobe Flash Player Install for all versions