The flaw could be potentially exploited by threat actors to carry out phishing attacks and other malicious activities.
According to an analysis conducted by LiveOverflow, the XSS vulnerability was apparently introduced on September 26, 2018, when a sanitization mechanism was removed after the review of the user interface design.
The design change was reverted on February 22, 2019, Google confirmed to have quickly addressed the vulnerability shortly after learning of its existence.
The analysis of the comments posted by developers when the change was reverted revealed that the bug was related to an HTML sanitizer. The issue was the root cause of the introduction of an XSS flaw in the Google Web Server (GWS) software.
Experts at LiveOverflow speculated the vulnerability likely affected other Google products that use the Closure library.
LiveOverflow has published a video PoC for the vulnerability: