What does "corruption" refer to in this verse?

Imām Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

1. Disbelief. [Ibn ʿAbbās]
2. Committing sins. [Abū al-ʿĀliyah and Muqātil]
3. Both disbelief and sins. [Al-Suddī from his teachers]
4. Neglecting to follow commands and avoid prohibitions. [Mujāhid]
5. How they mixed with the disbelievers, disclosing to them the secrets of the believers. [ʿAlī ibn ʿUbayd Allāh]