Advisories for Gem/Decidim-Core package

2026

Decidim amendments can be accepted or rejected by anyone

The vulnerability allows any registered and authenticated user to accept or reject any amendments. The impact is on any users who have created proposals where the amendments feature is enabled. This also elevates the user accepting the amendment as the author of the original proposal as people amending proposals are provided coauthorship on the coauthorable resources.

Decidim amendments can be accepted or rejected by anyone

The vulnerability allows any registered and authenticated user to accept or reject any amendments. The impact is on any users who have created proposals where the amendments feature is enabled. This also elevates the user accepting the amendment as the author of the original proposal as people amending proposals are provided coauthorship on the coauthorable resources.

Decidim's private data exports can lead to data leaks

Private data exports can lead to data leaks in cases where the UUID generation causes collisions for the generated UUIDs. The bug was introduced by #13571 and affects Decidim versions 0.30.0 or newer (currently 2025-09-23). This issue was discovered by running the following spec several times in a row, as it can randomly fail due to this bug: $ cd decidim-core $ for i in {1..10}; do bundle exec rspec …

2024

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Decidim is a participatory democracy framework. Starting in version 0.27.0 and prior to versions 0.27.5 and 0.28.0, the dynamic file upload feature is subject to potential cross-site scripting attacks in case the attacker manages to modify the file names of the records being uploaded to the server. This appears in sections where the user controls the file upload dialogs themselves and has the technical knowledge to change the file names …

2023

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Decidim is a participatory democracy framework, written in Ruby on Rails, originally developed for the Barcelona City government online and offline participation website. The external link feature is susceptible to cross-site scripting. This allows a remote attacker to execute JavaScript code in the context of a currently logged-in user. An attacker could use this vulnerability to make other users endorse or support proposals they have no intention of supporting or …

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Decidim is a participatory democracy framework, written in Ruby on Rails, originally developed for the Barcelona City government online and offline participation website. The processes filter feature is susceptible to Cross-site scripting. This allows a remote attacker to execute JavaScript code in the context of a currently logged-in user. An attacker could use this vulnerability to make other users endorse or support proposals they have no intention of supporting or …