In versions of the @theia/plugin-ext component of Eclipse Theia prior to 1.18.0, Webview contents can be hijacked via postMessage().

In Eclipse Theia 0.1.1 to 0.2.0, it is possible to exploit the default build to obtain remote code execution (and XXE) via the theia-xml-extension. This extension uses lsp4xml (recently renamed to LemMinX) in order to provide language support for XML. This is installed by default.

In Eclipse Theia 0.3.9 to 1.8.1, the "mini-browser" extension allows a user to preview HTML files in an iframe inside the IDE. But with the way it is made it is possible for a previewed HTML file to trigger an RCE. This exploit only happens if a user previews a malicious file..

In Eclipse Theia versions up to and including 1.8.0, in the debug console there is no HTML escaping, so arbitrary Javascript code can be injected.

In Eclipse Theia versions up to and including 0.16.0, in the notification messages there is no HTML escaping, so Javascript code can run.

In Eclipse Theia versions up to and including 1.2.0, the Markdown Preview (@theia/preview), can be exploited to execute arbitrary code.

In Eclipse Theia versions 0.3.9 through 0.15.0, one of the default pre-packaged Theia extensions is "Mini-Browser", published as "@theia/mini-browser" on npmjs.com. This extension, for its own needs, exposes a HTTP endpoint that allows to read the content of files on the host's filesystem, given their path, without restrictions on the requester's origin. This design is vulnerable to being exploited remotely through a DNS rebinding attack or a drive-by download of a carefully crafted exploit.

XMLLanguageService.java in XML Language Server (aka lsp4xml) before 0.9.1, as used in Red Hat XML Language Support (aka vscode-xml) before 0.9.1 for Visual Studio and other products, allows a remote attacker to write to arbitrary files via Directory Traversal.

XML Language Server (aka lsp4xml) before 0.9.1, as used in Red Hat XML Language Support (aka vscode-xml) before 0.9.1 for Visual Studio and other products, allows XXE via a crafted XML document, with resultant SSRF (as well as SMB connection initiation that can lead to NetNTLM challenge/response capture for password cracking). This occurs in extensions/contentmodel/participants/diagnostics/LSPXMLParserConfiguration.java.