Mouse side buttons open tabs after a firmware update?

If your mouse side buttons are opening tabs after a firmware update, a button mapping or profile may have changed. The update may also have exposed a problem in the mouse software or coincided with a browser setting change.

First, check what each button does outside your usual browsing. Then compare the result with the mouse's assigned actions before changing or reinstalling anything.

Check what the side buttons send

Open the Mouse Test. Save any unfinished work in other tabs first, since a side button may navigate away from the page.
Place the pointer over the test area and press each side button once. Note whether the test recognizes a mouse button and whether a tab opens or the page changes.
Test the left, right and wheel buttons separately. If a side button produces the same response as another button, note which one.
In a separate tab, open two harmless pages in sequence. Move the pointer away from links and press each side button once to see whether it goes back, goes forward, opens a tab or does nothing.
If possible, repeat with another mouse on the same computer, then try the affected mouse on another computer. Use the same connection method where you can.

On some systems, the browser may handle a side-button press as navigation before the test can display it. If that happens, the test alone cannot tell you whether the mouse or software assigned the action.

What the result means

The current tab goes back or forward

Back and forward are common side-button assignments. They change the page in the current tab rather than opening a new tab. If that is not what you want, check the mouse's button assignments. A forward action will appear to do nothing if there is no page ahead in the tab's history.

A new tab opens

Look at what opens. A blank tab can suggest a new-tab keyboard shortcut was assigned to the button. If a link opens in a new tab only when the pointer is over it, the button may be acting like a middle click or a modified left click. These clues are not proof, so check the mapping before changing it.

The test shows a different mouse button

A side button that registers like the wheel or a left click may have been reassigned in mouse software or an onboard profile. Check the assignments and any active profile. Also test without holding another mouse button or keyboard key.

The behavior changes between computers or apps

If the mouse behaves differently in another browser or app, an app-specific profile, browser extension or shortcut may be involved. If it behaves differently on another computer, compare the installed mouse software and settings. Some mice also store assignments onboard, so a setting can follow the mouse between computers.

How to stop the unwanted tabs

Check the active mouse profile. Open the software used to configure your mouse, if it has any. Look for the active profile and the assignments for the two side buttons. An update may have changed which profile is active or restored a different assignment.
Restore the actions you want. Assign each side button to back, forward or another supported action. Check for assignments such as middle click, a keyboard shortcut or a recorded sequence of actions. Save or apply changes if the software requires it, then repeat the test.
Check app-specific profiles. Some mouse software switches profiles when a particular app is active. Compare the browser's profile with the general profile, and check both side buttons. If the mouse supports onboard profiles, check which one is active too.
Rule out a held key. On Windows, Ctrl plus a click on a link can open it in a new tab. On a Mac, Command plus a click can do the same. Make sure neither key is stuck, and test without touching the keyboard.
Check the browser. Try the same buttons in a different browser. If the problem occurs in only one, temporarily disable its extensions one at a time and retest. Reenable any that do not affect the behavior.
Reconnect the mouse. For a wired mouse or USB receiver, try another USB port without a hub. For Bluetooth, disconnect and reconnect the mouse. Check its battery or charge if it is wireless, then restart the computer if the problem persists.

Windows and macOS have general mouse settings, but they may not offer assignments for extra buttons. You can check the primary button under Settings › Bluetooth & devices › Mouse in Windows 11 or System Settings › Mouse on a Mac. Use the mouse's configuration software for side-button assignments when it supports them.

Should you reinstall the firmware?

Not as a first step. Record your current assignments and profiles before resetting or changing them, because a reset may erase custom settings. If the problem began immediately after the update and the checks above do not help, consult the mouse maker's instructions for your exact model.

Reinstall or roll back firmware only if the maker provides and supports that procedure. Follow its power and connection instructions carefully, and do not interrupt the update. On a managed work or school computer, ask your administrator before changing device software.

When to suspect the mouse

If the same button sends an unexpected action on multiple computers after you have checked its saved assignments, the mouse may have a firmware or hardware fault. A button that also triggers without being touched, or fails intermittently, is another reason to contact the manufacturer or check the warranty. A repair shop or replacement may be the practical next step.

For a broader check of side-button behavior after an update, see mouse back and forward buttons after a firmware update.