Twitter is recruiting the help of the HackerOne community to try and fix troubling biases with its AI models.

The image-cropping algorithm used by Twitter was intended to keep the most interesting parts of an image in the preview crop in people’s timelines. That’s all good, until users found last year that it favoured lighter skin colours over dark and the breasts and legs of women over their faces.

When researchers fed a picture of a black man and a white woman into...