18;write_to_target_document1a;_fSnuaYnZLayZnesPw72ogAw_10;56;

As of the most recent official release, the for the Tenda F3 is:

18;write_to_target_document1a;_fSnuaYnZLayZnesPw72ogAw_20;56; 0;10c2;0;aa9;

Contact Tenda support via email or live chat. Alternatively, check their official community forum for beta releases.

Where to Find the Latest Firmware (Free) Official manufacturer sites provide firmware downloads at no cost. For the Tenda F3:

Note: If the links above don't work, the file may have been relocated. Go to https://www.tendacn.com → Search "F3" → Support → Firmware.