Não é um caso de sequestro de navegador / DNS. O que está acontecendo no seu caso é o que é chamado de Typosquatting .
De Wikipedia :
Typosquatting
Typosquatting, also called URL hijacking, a sting site, or a fake URL, is a form of cybersquatting, and possibly brandjacking which relies on mistakes such as typos made by Internet users when inputting a website address into a web browser. Should a user accidentally enter an incorrect website address, they may be led to any URL (including an alternative website owned by a cybersquatter).
The typosquatter's URL will usually be one of five kinds, all similar to the victim site address (e.g. example.com):
- A common misspelling, or foreign language spelling, of the intended site: exemple.com
- A misspelling based on typos: examlpe.com
- A differently phrased domain name: examples.com
- A different top-level domain: example.org
- An abuse of the Country Code Top-Level Domain (ccTLD): example.cm by using .cm, example.co by using .co, or example.om by using .om. A person leaving out a letter in .com in error could arrive at the fake URL's website.
Once in the typosquatter's site, the user may also be tricked into thinking that they are in fact in the real site, through the use of copied or similar logos, website layouts or content. Spam emails sometimes make use of typosquatting URLs to trick users into visiting malicious sites that look like a given bank's site, for instance.
Você encontrará muitos desses sites com os nomes de sites populares (como o github no seu caso), mas usando o domínio .cm em vez de .com
De Wikipédia :
.cm is the country code top-level domain (ccTLD) for Cameroon.
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In a report published in December 2009 by McAfee, "Mapping the Mal Web - The world's riskiest domain", .cm was reportedly the riskiest domain in the world, with 36.7% of the sites posing a security risk to PCs. It is widely assumed that malicious domain programmers rely on inadvertent misspellings of well-trafficked websites ending in ".com" to lure unsuspecting users to their domains
E apenas para verificar se não há problemas com seu navegador ou DNS, insira um endereço sem sentido no navegador, como link , e veja ele não redireciona para um site do tipo malicioso semelhante.