Blue high light expands the multiline text field borders - please see attached screen shot for details.

To reproduce:
- Open attached project and launch "test" scene
- Select the Main Camera object in Hierarchy
- Go to Inspector and click in the "My text" text field
- Observe the blue square of highlight

OR

1. Create a new game object and add the "My Text" component
2. Write some text in the "My Text" field
3. Copy the text > press Shift Enter > paste the text
4. Repeat step 3 multiple times
5. Click somewhere outside the component
6. Go to Inspector and click in the "My text" text field and observe the blue square of highlight