Tens a certeza que
todas as extensões têm acesso a
tudo ?
Nomeadamente homebanking que é algo particularmente sensível ?
Numa pesquisa rápida:
"there is an all-encompassing permission to "read and change all your data on the websites you visit" that is wildly prevalent; Huele found it in 71 percent of the top 500 extensions in the Chrome store. Read that permission again and really think about what it means."
in: "
https://www.popularmechanics.com/technology/security/a16741/browser-extension-security/"
71% é uma percentagem elevada, mas não é 100%.
Seja como for estou a seguir os vossos conselhos (kinda of [

]).
Neste momento já só tenho o uBlock Origin no Chrome.
1.
TODAS têm acesso a TUDO (onde correm).
Ou seja, para uma extensão ter o efeito pretendido, tem de correr na página onde é suposto ter o efeito pretendido, e quando corre nessa página, tem acesso a TUDO o que está na página (ler e modificar).
Uma extensão para bloquear pub corre normalmente automaticamente em TODAS as páginas de TODOS os sites... INCLUINDO HOMEBANKING.
2.
Esses 29% que faltam aos 71% poderão ser extensões que são feitas por determinados sites, e só funcionam nesses sites (restrição por URL onde corre).
Ainda assim, continuam a ter a permissão de LER E MODIFICAR TUDO (só não correm em todos os sites).
Normalmente existe no Chrome a opção de correr automaticamente ou manualmente. Manualmente, é necessário clicar na extensão para a executar na página corrente. Automaticamente corre sempre que uma página carrega. E isto pode ser restringido às páginas de um (ou mais) domínio, por exemplo. No entanto, quando a extensão corre, tem sempre acesso a tudo o que está na página, e pode modificar o que lá estiver. E quando corre, fica lá a correr até a página fechar.
Exemplo:
Uma extensão que seja para fazer qualquer coisa no GMail, e que por isso tenha no manifesto para correr apenas em "https://mail.google.com". Pode ler e modificar TUDO o que está nas páginas que estiveres a ver no GMail, mas não tem acesso a nada que esteja noutros URL que não comecem por "https://mail.google.com". Portanto, terá a permissão de "LER E MODIFICAR TUDO" na mesma... só não é em "ALL SITES", será em todas as páginas de "https://mail.google.com".
É como eu te disse, uma extensão é um programa escrito em JAVASCRIPT que tem acesso a ler e modificar TUDO o que estiver nas páginas onde é executado.
É esse o propósito de uma extensão do browser, e é assim que funciona.
O exemplo dos blockers de publicidade é o melhor desses exemplos, pois sem LER não conseguiria saber qual a publicidade a bloquear, e sem MODIFICAR não poderia impedi-la de aparecer.
Alguns browsers têm a possibilidade de dar permissões ADICIONAIS (câmara, microfone, GPS, ficheiros, etc.), como é o caso do Chrome.
Tens aqui uma lista das permissões, e um exemplo de um manifesto que "apenas" dá acesso a LER E MODIFICAR TUDO de páginas que estejam nos domínios BLOGGER.COM e GOOGLE.COM.
https://developer.chrome.com/extensions/declare_permissions
O default é ler e modificar tudo para todo o conteúdo de todas as páginas de TODOS os domínios. O menor que podes ter é ler e modificar tudo de todo o conteúdo de todas as páginas de um domínio, e execução manual da extensão.
https://en.wikipedia.org/wiki/Browser_extension#Unwanted_behavior
(...)
Browser extensions typically have access to sensitive data, such as browsing history, and have the ability to alter some browser settings, add user interface items, or replace website content.[20][21] As a result, there have been instances of malware, so users need to be cautious about what extensions they install.[22][23][24][25]
There have also been cases of applications installing browser extensions without the user's knowledge, while making it hard for the user to uninstall the unwanted extension.[26]
Some Google Chrome extension developers have sold their extensions to third-parties who then incorporated adware.[27][28] In 2014, Google removed two such extensions from the Chrome Web Store after many users complained about unwanted pop-up ads.[29] The following year, Google acknowledged that about five percent of visits to its own websites had been altered by extensions with adware.[30][31][32]
(...)
https://www.wired.com/story/chrome-extension-malware/
(...)
“What we’re seeing is an increase in criminal use of extensions,” says William Peteroy, CEO of the security firm Icebrg. “And when we start to see criminal pickup on things it absolutely meets our bar that this is something we need to pay attention to, and something users need to start paying a lot more attention to than they are right now.”
(...)
Other browsers suffer a similar onslaught, but with almost 60 percent market share, attacks on Chrome users will generally affect the largest number of people, making it a prime target for criminal hackers. Icebrg recently highlighted four malicious extensions in the Chrome Web Store that had more than 500,000 downloads combined. The extensions masqueraded as standard utilities, with names like “Stickies” and “Lite Bookmarks.” The researchers saw indications, though, that they were actually part of click-fraud scams to boost revenue for attackers. And the extensions requested enough privileges that they could have snooped even more, accessing things like user data, and tracking their behavior. Google removed the four extensions after Icebrg disclosed them privately.
(...)
Part of the problem: Chrome is already a trusted application. When users give it permission to run certain code, like an extension, their operating system and most antivirus products usually give it a free pass. And the more systems and services move into the browser—like Microsoft 365 and Google’s G Suite—the more valuable data and network access a malicious Chrome extension could potentially get.
In addition to distributing malicious apps through mechanisms like phishing and compromised sites, attackers have also refined techniques to smuggle their extensions into the Chrome Web Store, and then modify them remotely once downloaded to add or activate nasty features.
In October, Google removed three extensions impersonating AdBlock Plus, one of which had almost 40,000 downloads. That same month, researchers at Morphus Labs discovered an extension, dubbed “Catch-All,” that launched from a phishing attempt targeting WhatsApp users, mimicked an Adobe Acrobat installer, and then captured all the data users entered while browsing in Chrome once installed, including usernames and passwords.
In December, researchers at the internet security firm Zscaler found an extension that lifted login credentials, cookies, and financial data from users who visited and logged into Banco do Brasil websites and accounts. And this month, the software security company Malwarebytes published findings about an extension (built for both Chrome and Firefox) called “Tiempo en colombia en vivo” that forced itself to install when users visited compromised web pages and then was deviously difficult to uninstall. Malwarebytes researcher Pieter Arntz said that he couldn’t even completely analyze what the extension’s operations and goals were, because it was coded with extensive obfuscation.
(...)
“I think the exposure is huge,” says Jake Williams, a penetration tester and malware analyst who founded Rendition Infosec. “It's trivial for an attacker to get their extension published and then change the behavior dynamically after it's published."
(...)
“What we saw in our research was that this was undetected and active across a large swath of enterprises,” Icebrg’s Peteroy says. “They’re successful in bypassing Google’s efforts to create security around extensions. And because extensions run at the application layer, running in the browser, it completely bypasses a lot of protections.”
(...)
https://www.howtogeek.com/188346/wh...can-be-dangerous-and-how-to-protect-yourself/
(...)
In August 2017, the very popular and widely recommended Web Developer extension for Chrome was hijacked. The developer fell for a phishing attack, and the attacker uploaded a new version of the extension that inserted more advertisements into web pages. Over a million people who trusted the developer of this popular extension ended up getting the infected extension. As this is an extension for web developers, the attack could have been a lot worse—it doesn’t appear that the infected extension functioned as a keylogger, for example.
(...)
In many other situations, someone develops an extension that gains a large amount of users, but doesn’t necessarily make any money. That developer is approached by a company that will pay a large amount of money to purchase the extension. If the developer accepts the purchase, the new company modifies the extension to insert advertisements and tracking, uploads it to the Chrome Web Store as an update, and all the existing users are now using the new company’s extension—with no warning.
This happened to Particle for YouTube, a popular extension for customizing YouTube, in July 2017. The same thing has happened to many other extensions in the past. Chrome extension developers have claimed they constantly receive offers to buy their extensions. The developers of the Honey extension with over 700,000 users once ran an “Ask Me Anything” on Reddit, detailing the kind of offers they often receive.
(...)
Chrome has been under attack due to its popularity, but this problem affects all browsers. Firefox is arguably even more at risk, since it doesn’t use a permission system at all—every extension you install gets full access to everything.
(...)
It’s also important to only use extensions from companies you trust. For example, an extension for customizing YouTube created by a random person you’ve never heard of is a prime candidate for becoming malware. However, the official Gmail Notifier created by Google, OneNote note taking extension created by Microsoft, or LastPass password manager extension created by LastPass will almost certainly not be sold to a shady company for a few thousand bucks.
(...)
However, the developer fell for a phishing attack and the extension became malicious. It’s a good reminder that, even if you could trust someone not to sell their extension to a shady company, you’re relying on that person for your security. If that person slips up and allows their account to be hijacked, you’ll end up dealing with the consequences—and they could be a lot worse than what happened with the Web Developer extension.
(...)