TYPO3 Core

Resources/Public/Css/main.css

.typo3-extension-list th:hover {
  background: rgba(200, 200, 200, 0);
}

this rule is generated from

Resources/Private/Scss/page/_manage.scss

// Table
.typo3-extension-list {
    th {
        &:hover {
            background: rgba(200,200,200,.3);
        }
    }
}

Obviously SASS was dropping the .3 in some version (the current version doesn't)

Chrome ignores the :hover rule altogether, Opera shows it correctly (defacto hiding the header)

As the instructions for generating the main.css file are faulty (the output has closing brackets on the same line as the last rule), I cannot provide a "generated" patch for gerrit.

As a side note: If there is a flag for SASS missing, why is that not documented in the README.txt?