Yes: a browser extension with the necessary access to a web messenger can read message text after the page decrypts and displays it. That does not require breaking the encryption used between participants. It is access to one of the endpoints where the content is already readable.
Not every extension can read every site. The risk depends on granted permissions, the extension's behavior and the browser environment. Review that scope rather than assuming either that all extensions are spyware or that an official-store listing removes the risk.
How content scripts see a page
Chrome's content-script documentation explains that content scripts can read and modify the page's Document Object Model, or DOM, on sites they are permitted to access.
These scripts normally run in an isolated JavaScript world: their variables are separate from the page's variables. However, the page's DOM is still a shared surface. If a chat message or draft is present there, isolation of JavaScript variables is not a promise that the extension cannot read that text.
This distinction matters because an extension need not steal a private encryption key to capture a readable message. Nor does ordinary site access automatically grant every possible capability, such as unrestricted access to all browser cookies; those details depend on additional permissions and interfaces.
Why E2EE does not solve endpoint access
End-to-end encryption protects content between authorized endpoints. The application must make received content available to the person reading it, and a compromised or over-permissioned local environment can access that readable copy.
The cryptographic boundary is not simply “the network socket,” and E2EE is more than transport encryption. But it is not a general defense against software that can observe the authorized endpoint's output or input.
For the same reason, upgrading to a post-quantum key exchange does not stop a permitted extension from reading a draft before it is encrypted.
Controls that help, and claims to avoid
| Control | What it can help with | What it does not guarantee |
|---|---|---|
| Restricted extension site access | Limits where permitted scripts can operate | That the extension is trustworthy on sites still allowed |
| A separate profile with no added extensions | Reduces extension exposure for that profile | Protection from operating-system malware or a compromised browser |
| Web Workers or non-exportable keys | Can reduce particular key-handling risks | Confidentiality of plaintext later displayed to the user |
| Content Security Policy | Restricts certain page script/resource behavior | A universal barrier against browser-authorized extensions |
| Shadow DOM or canvas rendering | Changes rendering and encapsulation | A reliable security boundary against hostile local software |
Manifest V3 changes extension capabilities and rules, but it does not remove the documented ability of permitted content scripts to inspect a page. Claims that a rendering technique makes a messenger “extension-proof” need much stronger evidence.
Review Chrome permissions before a sensitive chat
Use Chrome's extension-management guide to review installed extensions and their site access. Where the feature is available, restrict access to the sites actually needed or require activation on selection. Remove extensions you no longer use.
Pay attention to permission changes, but do not assume every harmful update must request new permissions. Code can misuse access it already has. Chrome's permission-warning documentation explains when added permissions trigger a warning.
Incognito is not automatically an extension-free environment: Chrome allows individual extensions to be enabled there. Check the actual configuration. Likewise, do not apply a Chrome web-page claim indiscriminately to a standalone desktop app with a different runtime.
If you suspect an extension exposed messages
Stop using the affected environment for sensitive communication. Disable or remove the suspect extension, update the browser and review its remaining extensions and permissions. From a trusted environment, review account sessions and follow the service's recovery guidance if credentials or account access may have been exposed.
Removing an extension prevents its future operation in that browser; it cannot recall content already copied. A clean-looking chat history is not proof that no disclosure occurred.
Livara's boundary
Livara's threat model explicitly excludes protection against a compromised endpoint. Its Proof Lab offers an APK hash check and a bounded cryptography demonstration, not a certification that the browser session is free of malicious extensions.
Keep the extension permission boundary as small as practical. Strong message encryption and a trustworthy endpoint are complementary requirements.
