Updating firmware on Technicolor TG582n

[#1]

I've just run a scan with Avast which has indicated that my router is vulnerable to threats and that this may be due to outdated firmware (I currently have software release 10.2.2.B). Can this be done remotely by PlusNet?
I've copied the Avast output below.

Quote

Description Our scan has found your router vulnerable to attacks. That is, the router contains a problem that can be misused by cybercriminals to break into your network and compromise your security and privacy. Solution Some of the vulnerabilities are patched in new versions of the device firmware. Therefore, applying the latest firmware update may solve the problem. Routers typically do not perform automatic updates, so the process requires appropriate patches to be manually downloaded and installed on the device. Consult your router's manual for instructions to download the latest firmware and apply it to your router. Done incorrectly, this can make your router unusable. Therefore we recommend that this procedure is done only by very advanced users or computer technicians. Details We have identified the following problems with your router: ROM-0 Severity: High This vulnerability allows an attacker to easily gain control of the router and therefore your Internet connection. The attacker can use a specially crafted HTTP request to download all important and secret data stored in your router -- your router login/password combination, your Wi-Fi password and your configuration data. To overcome this vulnerability, aside from applying the firmware update that addresses the issue, there is one more technique that can be used: setting up port forwarding for port 80 on the router to an unused IP address on your network. To do that, enter your router configuration page and find the "Port forwarding" section. Here, set up a rule that tells the router to send all http traffic to an unused local IP address (for example 192.168.0.255, if this address is not used by any other device on the network).

[#2]

I don't think the ROM-0 vulnerability is applicable to Technicolor routers. Perhaps it is a false positive. Is there any chance Avast found some other device, like a wireless repeater / booster?
You could also use a website like http://canyouseeme.org/ to check if port 80 is open to the Internet.

[#3]

Thanks for your reply ejs. I've actually just checked the Avast web forums and it looks like it might be a false positive after all: https://forum.avast.com/index.php?topic=181612.0 . I tested it by running a before and after update scan on a laptop that hadn't been used for a few days, and only got the message after installing the most recent update.
I checked port 80 on canyouseeme.org and it comes up with the error message "Error: I could not see your service on [IP HERE] on port (80)", which I guess means that closed.