Deal with images of different aspect ratio inside grids

.posters  {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(150px, auto)); // fluid grid
  justify-content: center;
  gap: 3px;
  max-width: 1300px;
  margin: 0 auto;
}

.poster {
  position: relative;
  background-color: red;
}

.poster__image {
  width: 100%;
  height: 100%; // solves the problem, but Lighthouse gives me a warning about the image not having the original ratio
}