A recently patched security flaw in the Opera web browser, identified as CrossBarking, posed a significant threat by allowing malicious extensions to gain unauthorized access to private APIs. According to Guardio Labs, this vulnerability could have enabled various malicious actions, including capturing screenshots, modifying browser settings, and hijacking user accounts.
The demonstration of this issue involved publishing a seemingly harmless browser extension on the Chrome Web Store, which could exploit the flaw when installed on Opera, illustrating the potential for a cross-browser-store attack. This incident highlights the persistent struggle between user productivity and security, shedding light on the tactics employed by modern threat actors who operate under the radar.
The security flaw has raised alarms due to the privileged access that several publicly accessible subdomains owned by Opera have to private APIs embedded within the browser. These domains support various Opera-specific features, such as Opera Wallet and Pinboard, as well as internal development functions. Guardio’s research indicated that content scripts within browser extensions could be manipulated to inject malicious JavaScript into these permissive domains, thereby gaining access to private APIs.
This access could be exploited by attackers to take screenshots of open tabs, extract session cookies for account hijacking, and modify critical settings, such as DNS-over-HTTPS configurations. While the flaw has been addressed by Opera as of September 24, 2024, the incident is not an isolated occurrence; earlier vulnerabilities have also been identified in the browser. In January, a different security issue known as MyFlaw was reported, which exploited a legitimate feature called My Flow to execute files on users’ operating systems.
The combination of these vulnerabilities underscores the need for users to exercise caution when installing browser extensions, particularly those from third-party sources, as rogue extensions have increasingly infiltrated official stores. Guardio Labs emphasized the importance of robust monitoring and verification processes for browser extensions to prevent such vulnerabilities from being exploited in the future.
They recommended that policy enforcers enhance the current review model by increasing manpower and employing continuous activity analysis post-approval. Additionally, implementing stricter identity verification for developers could help mitigate risks associated with malicious extensions. Although Opera stated that there is no evidence of this particular vulnerability being exploited in the wild, the incident serves as a critical reminder of the need for ongoing vigilance in securing web browsers and their extensions.
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