| Vol-3012 urn:nbn:de:0074-3012-6 Copyright © 2021 for the individual papers by the papers' authors. Copyright © 2021 for the volume as a collection by its editors. This volume and its papers are published under the Creative Commons License Attribution 4.0 International (CC BY 4.0).

# OHARS 2021
Online Misinformation- and Harm-Aware Recommender Systems

### Proceedings of the Second Workshop on Online Misinformation- and Harm-Aware Recommender Systems
co-located with 15th ACM Conference on Recommender Systems (RecSys 2021)

### Virtual Event, Amsterdam, The Netherlands, October 2, 2021.

Edited by

### Antonela Tommasel *
Daniela Godoy *
Arkaitz Zubiaga **

* ISISTAN Research Institute (CONICET / UNICEN), Tandil, Argentina
** Queen Mary University of London, UK

## Table of Contents

- Second Workshop on Online Misinformation- and Harm-Aware Recommender Systems: Preface i-iv
  Antonela Tommasel, Daniela Godoy, Arkaitz Zubiaga

### Research Papers

- “To trust a LIAR”: Does Machine Learning Really Classify Fine-grained, Fake News Statements? 1-13
  Mark Mifsud, Colin Layfield, Joel Azzopardi, John Abela
- The Privacy versus Disclosure Appetite Dilemma: Mitigation by Recommendation 14-32
  Rim Ben Salem, Esma Aïmeur, Hicham Hage
- Adversarial Attacks against Visual Recommendation: an Investigation on the Influence of Items' Popularity 33-44
  Vito Walter Anelli, Tommaso Di Noia, Eugenio Di Sciascio, Daniele Malitesta, Felice Antonio Merra
- An Empirical Analysis of Collaborative Recommender Systems Robustness to Shilling Attacks 45-57
  Anu Shrestha, Francesca Spezzano, Maria Soledad Pera
- User Polarization Aware Matrix Factorization for Recommendation Systems 58-67
  Wenlong Sun, Olfa Nasraoui
- PaRIS: Polarization-aware Recommender Interactive System 68-75
  Mahsa Badami, Olfa Nasraoui

2021-11-10: submitted by Daniela Godoy, metadata incl. bibliographic data published under Creative Commons CC0
2021-11-16: published on CEUR Workshop Proceedings (CEUR-WS.org, ISSN 1613-0073) |valid HTML5|