On April 23, Canonical published, in a security notice, details about an IcedTea-Web regression for its Ubuntu 12.04 LTS and Ubuntu 11.10 operating systems.
According to Canonical, IcedTea-Web was unable to access some sites, due to a regression introduced in a previous update.
The USN-1804-1 patch fixed vulnerabilities in IcedTea-Web. It introduced a regression, with the Java Network Launching Protocol (JNLP), when fetching content over SSL under certain configurations, such as when using the community-supported IcedTead 7 browser plugin.
For a more detailed description of the security problems, you can visit Canonical's security notification.
The security flaws can be fixed if you upgrade your system(s) to the latest icedtea-netx package, specific to each distribution. To apply the update, run the Update Manager application.
In general, a standard system update will make all the necessary changes. A system restart will not be necessary to implement the changes.