TYPO3 Core

Good catch!
Reproducible in v10 on every second row when adding class="insecure" to them. Seems the even/odd handling takes CSS precedence ...

Needs to be fixed in _extensionmanager.scss:

Solution A:

.extension-list {
    &.table-striped .insecure {
        background-color: #ffd9d9;
    }
}

Solution B:

#typo3-extension-list .insecure {
    background-color: #ffd9d9;
}

The fix is necessary for v10 but not for v11 (master)