Exposure compensation sets incorrectly - Nikon D300 Body Only Digital Camera

Is this a Fuji camera?
Check to make sure you have not set an aperture correction override. (Exposure compensation setting) Also check the metering mode or Exposure mode. You may also have the sensitivity set incorrectly. If this is the Fuji XT20 there are three exposure sensitivities setting it too high will cause this problem I expect.

Your exposure compensation might not be set correctly. Just behind and to the right of the on/off switch you will see a small button with a "+/-" symbol. That is the exposure compensation switch. When you press it, you will see a number displayed on the LCD. If the number is positive, that is your problem. Positive numbers increase exposure and negative numbers decrease exposure. Set the compensation to 0.0 by turning the rear thumbwheel while depressing the exposure compensation button.

It sounds like you've got exposure bracketing turned on. Hold down the Fn button and turn the main command dial to change the number of shots to 0.
Full details are in the "Bracketing" subsection of the "Exposure" section of the manual (page 130 in my copy). If you need a manual, you may download a copy here.

It sounds like you've got exposure bracketing turned on.
Refer to the "Bracketing" subsection of the "Exposure" section of the manual (page 130 in my copy). If you need a manual, you may download a copy here.

Yes, there is a setting called exposure compensation, which you may have altered.
Try switching the camera back to A (Auto) mode, and see if that fixes it.
In the manual setting modes, exposure compensation will look like this:
http://images.digitalcamerainfo.com/images/upload/Image/new/Photokina08/Canon/sd880is/photos/Canon-sd880is-menu-functionset-375.jpg
Make sure that you haven't set the exposure compensation to +2, for example. It should usually be set on 0.

When you change the exposure compensation setting, the camera will change the aperture, the shutter speed, or the ISO depending on the mode you're in and the shooting situation. That's what "compensation" means.

You are exposure compensation in manual mode. If you want the shots lighter, either open up the aperture or slow the shutter. The exposure compensation feature is to override the automatic settings determined by the camera in the auto-exposure modes.

Check the exposure compensation setting to ensure it's set for +/-0. To do this, set the camera for Program mode. Locate the exposure compensation mode button - it's the button with a +/- on it immediately behind the on/off switch. With the camera on, hold down this button. If it shows anything other than "0", use the main command dial (the wheel on the back) to change to setting to 0.

The reason the camera works in the Auto mode is because the exposure compensation settings are not available in auto mode, but are available in Program (P), Aperature (A) and Shutter (S) modes.

Check your exposure compensation adjustment. If that is set high, then all your shots will be over-exposed until it is brought down to the "0" setting. A relative had this problem with a different camera, and all it took was resetting the exposure compensation to make things work correctly.

I often set cameras with a default exposure compensation of -0.3 EV since blown highlights are so distracting.

The exposure compensation stays where you leave it unless you do a full reset or a custom reset, and except when you're using scene modes. But you don't need to do a reset to cancel out an exposure compensation -- simply use the exposure compensation button to adjust the compensation back to 0.0EV.