Valve recently patched a significant security flaw in Steam. However, just to be safe, it’s a good idea to double-check your account security and any available funds.
Yesterday, it was revealed that Steam was affected by a cross-site scripting (XSS) vulnerability that could compromise account security or be used to steal user data. Fortunately, the issue has been resolved, and viewing profiles and activity feeds is now safe. Kudos to Valve for promptly addressing this vulnerability.
A cross-site scripting vulnerability allows attackers to inject malicious code into websites that other users can view. While there are various methods and subtypes, the concept remains the same—an attacker exploits a web application to insert harmful data into a request for what should be “clean” information. The host website processes and delivers the malicious data as if it were valid, and the user’s browser accepts it as trustworthy, unaware that it contains harmful content.

It is unclear whether the issue was resolved server-side or whether a client update is required. To stay secure, we recommend checking for and installing any available updates. Moderator DirtDiglett, who created a proof of concept to highlight this exploit, explained that it could be used for various malicious purposes. The vulnerability could be triggered simply by visiting a malicious Steam profile page.
The attack could redirect users to fake, non-Steam pages designed to look like the Steam website, allowing attackers to steal login credentials in a phishing and malware combo attack. It could also exploit a logged-in account to spend marketing funds on behalf of the attacker or manipulate other page elements as desired.
Only profiles with a level of 10 or higher were affected, and the vulnerability was linked to Steam’s “My Guides Showcase.” Malicious scripts embedded in the title section of a guide were executed, though the “Favorite Guide” feature and single-guide showcases were not affected. This issue could create significant problems for many users despite these specific parameters.
If you suspect your account may have been affected by this issue, take the following steps:
1. Enable two-factor authentication for your account through Steam Guard.
2. Update your account password.
3.De-authorize all devices currently linked to your account.
4.Reset your cable modem and router to obtain a new IP address.
If you suffered financial loss from this attack, contact Steam Support immediately.