Discourse Spoiler-Alert

[Steven]

Here is the default css for the blur part

.spoiler-blurred img {
  filter: blur(1em);
}

Change the 1em to something more important

.spoiler-blurred img {
  filter: blur(5em);
}

And if you want to blur more when the cursor is on the image, add these line and change the 0.5em (with a value less important than the one before)

.spoiler-blurred {
  .discourse-no-touch & {
    &:hover, &:focus {
      img {
        filter: blur(0.5em);
      }
    }
  }
}