Open Source Point of Sale (opensourcepos) is a web based point of sale application written in PHP using CodeIgniter framework. opensourcepos 3.4.0 and 3.4.1 has a stored XSS vulnerability exists in the Configuration (Information) functionality. An authenticated user with the permission “Configuration: Change OSPOS's Configuration” can inject a malicious JavaScript payload into the Company Name field when updating Information in Configuration. The malicious payload is stored and later triggered when a user accesses /sales/complete. First select Sales, and choose New Item to create an item, then click on Completed . Due to insufficient input validation and output encoding, the payload is rendered and executed in the user’s browser, resulting in a stored XSS vulnerability. This vulnerability is fixed in 3.4.2.