Arduino IDE 2.x is an IDE based on the Theia IDE framework and built with Electron. A Self Cross-Site Scripting (XSS) vulnerability has been identified within the Arduino-IDE prior to version v2.3.5. The vulnerability occurs in the Additional Board Manager URLs field, which can be found in the Preferences -> Settings section of the Arduino IDE interface. In the vulnerable versions, any values entered in this field are directly displayed to the user through a notification tooltip object, without a proper output encoding routine, due to the underlying ElectronJS engine interpretation. This vulnerability exposes the input parameter to Self-XSS attacks, which may lead to security risks depending on where the malicious payload is injected. This vulnerability is fixed in 2.3.5.