My guess is that you are working with Lightroom, and that you had all of your images selected when you applied the crop to one image, thus syncing the crop settings to all images. You can always undo the crop in the history. Or select all images (besides those you want to keep the crop settings on, and reset the crop).
Additionally, you may have created a Develop Preset that includes crop settings and auto applying the preset when importing images. Check your import settings on the right side of the import window.